Kalafati Ranta

Combining 2 in 1, this tour is perfect for those visiting Mykonos as part of their cruise. Once you disembark, the local SeaBus welcomes and introduces you to the first coastal views of the picturesque Mykonos island. Soon, the torch is picked up by the Delos ferry, indicating the beggining of a once in a lifetime journey back in time with final destination: the island of Delos, the most famous and sacred of all islands in antiquity. A half-hour boat trip takes you to the historical Delos sanctuary, birthplace of Apollo and Artemis, Unesco's world heritage. Your guide shows you the ancient temples, mosaic floor villas, the Naxian Lions, the Roman amphitheater and more. This shared tour takes 5-hours overall and you are able to choose from one of two departure times when you book.

Explore Mykonos island with this 2to 4hrs private island tour. Discover hidden gems beyond the tourist hotspots and delve into the island's rich history. We will make several stops for photos and have some free time at Ano Mera Village. Pick up and drop off can be at your preferable place.

Come onboard and enjoy the breathtaking Mykonian sunset! Set sail and enjoy the magnificent view of Little Venice and Mykonos. Drop anchor to watch the "Dreamy Sunset" over the ocean, islands, and distant shoreline. Enjoy drinks and snacks on-board, before setting out on the return journey, where we relish the mesmerizing light of the sun setting over the Aegean Sea. This is a cruise that you will make memories to last a lifetime, as it is ideal for couples, families, friends or people who just want to have a relaxing and memorable time.

Visit with licensed guide the natural insular archaeological site of Delos and enjoy swimming and snorkeling to a secluded cove off the uninhabited island of Rhenia on a 6-hour yacht cruise with a yummy lunch and complimentary drinks. Experience the great combo of leisure and history in one single day. Discover why sailing is the ultimate way to experience Mykonos, famously known as the "Island of Winds". What You'll Do: • Discover the sacred island of Delos with Licensed English Speaking Guide • Swim and snorkel in the crystal clear waters of the uninhabited Rhenia Island • Savour a lunch of Greek flavours cooked on board with fresh ingredients and juicy local fruits • Treat your thirst with house wine, beers and soft drinks offered complimentary • Stay connected with free use of Wifi on board • Add pick-up & drop-off shuttle transportation for a stress-free getaway

Pick up from the Cruise Ship Terminal and embark on an unforgettable journey through Mykonos with a local guide! Begin your Shore Excursion enjoying magnificent views of the Aegean Sea and nearby islands—perfect for capturing stunning photos. See some beautiful beaches & head to Mykonos Town, where you’ll stroll through narrow streets lined with charming whitewashed houses and explore famous landmarks like the Windmills and Little Venice. Along the way, your expert guide will share fascinating insights into the island’s rich history, culture, and hidden gems, giving you an authentic Mykonos experience. Whether you're seeking breathtaking views, fascinating stories, or simply a chance to immerse yourself in local life, this tour has it all. Don't miss out on the opportunity to discover Mykonos like a true local. Book your tour half-day sightseeing tour today and experience the island’s magic!

Hop on board and live a unique cruise experience in Mykonos island. Sail to the ancient Delos, explore this UNESCO World Heritage site, swim in dazzling waters of Rhenia island and indulge in a freshly prepared meat and veggie BBQ on board.

Let your taste buds do the traveling during this 6-hour cooking class in Mykonos. Make an authentic Greek meal and then savor it with your fellow cooks, all under the friendly and helpful eye of a professional. Learn how to make classics such as stuffed peppers and spinach pie, and wash it all down with wine and drinks. There is also the option to add a farm or island tour or a walking tour of Mykonos Town. Don’t miss this chance to learn about an important part of Greek culture and become a member of a true Mykonian family.

Welcome to the ultimate experience in Mykonos town - a delightful combination of a Walking Tour and a Tasting Tour, offering a sensory journey through the charming streets and delicious flavors of this captivating Greek island. Wander through the labyrinthine alleys of Mykonos town, where each step unveils fascinating tales of the island's history, culture, and architecture. Admire the enchanting white-washed buildings, vibrant bougainvillea, and the iconic windmills The tour will then lead you to a charming local bakery and authentic street food shops for the Tasting Tour part of the experience. Indulge your taste buds in a tantalizing array of Greek delicacies and traditional dishes. Traditional Greek street food offers a delectable variety of dishes bursting with Mediterranean flavors. The duration is approx 3h If you need a private pick up let us know so we can give you informations

Swimwear party, next to the sea, in private beds-loungers, with champagne, dance rhythms, and incredible cocktails!! Want it? You got it! Visit two of the most famous beaches in Mykonos (Paradise & Super Paradise and have fun at the 4 best Beach Clubs in Mykonos : Tropicana, Paradise Beach Bar, Super Paradise Beach Bar & JackieO’

In our classes, you’ll learn how to make classic Greek dishes like tzatziki, cheese pies, spinach pies, dolmades, and even how to masterize the world known greek gyros experience by preparing the gyros meat and baking your own pita-bread. It’s a hands-on experience that lets you bring the flavors of Greece into your own kitchen. With the guidance of our professional chefs you will learn not only how to cook these delightful dishes but deeply understanding the essence of Greek cuisine. This journey is about combining techniques, flavours, aromas and cooking tips to create meals that celebrate life, culture, and the joy of sharing. Our chefs will walk you through each recipe, imparting valuable tips and sharing stories that showcase the spirit of Greek hospitality. Join us for a memorable cooking experience. Whether you’re a beginner or already know your way around the kitchen, you’ll leave with new skills and a deeper appreciation for Greek cuisine.

Explore Mykonos island with this 4hrs private island tour. Hidden beaches, famous attractions like Armenistis Lighthouse and Ano Mera Village and local places are some of the things you'll see with us. Our experienced guides and our luxury vehicles will make you feel comfortable and make this experience a time to remember! We will make several stops for photos and have some free time at Ano Mera Village for shopping and walking. Special requests can be accepted upon request and communication with the company in advance. The pick up and drop off can be at your preferable place free of charge.

Set off on an unforgettable journey through the captivating streets of Mykonos Town with a 2-hour walking tour. Perfect for travelers eager to dive into the spirit of this legendary Greek island, this experience invites you to savor the charm and beauty of its most iconic landmarks. Begin your adventure at the Old Port, pass by from Manto Mavrogenous Square and continue with the famous Mykonos Windmills, standing proudly as enduring symbols of the island’s rich heritage. Continue to the enchanting area of Little Venice, where colorful waterfront buildings seem to float at the edge of the sea. Finally, admire the architectural wonder of the Church of Panagia Paraportiani, one of the most photographed landmarks in Greece. Throughout the tour, your guide shares captivating stories and insights about Mykonos's everyday life.

What makes our product unique is the contact with sea & sun. Sailing away with Nadia K, you will have the opportunity to experience new adventures at the Aegean Sea and explore magical places at the Island of the Winds. Close your eyes, fill the sense of sun and wind, relax with the music and you’ll feel comfortable. Our visit to Unesco World Heritage site of Delos, is of great importance to get in touch and feel the pulse of Greek history and beauty! Then we reach the uninhabited island of Rhenia, where you can swim to crystal clear waters and explore the ocean bottom with the snorkeling gear , which is free for use onboard.

A unique journey through the authentic side of Mykonos on powerful 450cc-600cc quad bikes!we have experience up to 10 years at this object.. Our team is ready to guide you through every corner with a fresh, authentic perspective.

Experience the island discovery with our bespoke private tour. The journey begins in the heart of Chora, where the romantic charm of Little Venice meets the iconic silhouette of the Windmills. We explore the sculptural beauty of Paraportiani Church and wander the chic, white-washed corridors of Matoyianni Street. Leaving the bustle behind, we head to the rugged Faros Armenistis for sweeping Aegean views before discovering the serene northern shores of Panormos, the untouched sands of Agios Sostis, and the wind-swept beauty of Ftelia. We then dive into the island’s authentic heritage at Ano Mera Village, visiting the historic Monastery to glimpse traditional life. The coastal adventure continues to the crystalline waters of Kalafatis and the cosmopolitan shores of Kalo Livadi. Finally, we conclude with a breathtaking Panoramic view of Mykonos town, capturing the white labyrinth against the deep blue harbor—a perfect finale to your personalized Greek escape.

We setsail at 09:00am from Tourlos Marina. Our first stop is an hour away, the renowned Big Delos island. While there, you will have the opportunity to visit one of the most famous archaeological sites in Greek history : the birthplace of the Olympian God Apollo and the Olympian Goddess Artemis. You will have approximately one hour to explore the grounds of this significant cult center of Ancient Greece. Back on the boat, we will treat you to a traditional Mykonian lunch while you enjoy a drink of your choice, before sailing to the island of Rhenia. Rhenia is four times the size of its sacred sister Delos, and they are separated by a small channel. Rhenia is uninhabited and has four solitary sandy beaches (Glyfada, Stena, Lia and Ambelia) which rest in protected coves. Rhenia is a popular meeting point for yachts cruising the area due to its spectacular waters, which range in colour from a stunning emerald green to a beautiful turquoise blue.

Located in Ano Mera, in the heart of the island, the Mykonian Farm is the perfect choice to discover and to taste the finest Greek wines. Choose from a 12pm or 6pm departure time when you book, and you will not only learn the basic tasting techniques, but you will uncork and savor Greece’s most distinct blends.

Welcome to the enchanting Mykonos Town, where azure waters meet white-washed buildings and cobblestone streets. Mykonos Town is not only a visual masterpiece but also a culinary haven waiting to be explored. Join one of our signature walking tour as we wind through iconic landmarks and hidden alleys, uncovering local secrets and sampling the finest Greek delights Mykonos has to offer on an unforgettable Food Tour.

Come onboard and enjoy the breathtaking Mykonian sunset! Set sail and enjoy the magnificent view of Little Venice and Mykonos. Drop anchor to watch the "Dreamy Sunset" over the ocean, islands, and distant shoreline. Enjoy drinks and snacks on-board, before setting out on the return journey, where we relish the mesmerizing light of the sun setting over the Aegean Sea. This is a cruise that you will make memories to last a lifetime, as it is ideal for couples, families, friends or people who just want to have a relaxing and memorable time.

Visit with licensed guide the natural insular archaeological site of Delos and enjoy swimming and snorkeling to a secluded cove off the uninhabited island of Rhenia on a 6-hour yacht cruise with a yummy lunch and complimentary drinks. Experience the great combo of leisure and history in one single day. Discover why sailing is the ultimate way to experience Mykonos, famously known as the "Island of Winds". What You'll Do: • Discover the sacred island of Delos with Licensed English Speaking Guide • Swim and snorkel in the crystal clear waters of the uninhabited Rhenia Island • Savour a lunch of Greek flavours cooked on board with fresh ingredients and juicy local fruits • Treat your thirst with house wine, beers and soft drinks offered complimentary • Stay connected with free use of Wifi on board • Add pick-up & drop-off shuttle transportation for a stress-free getaway

Hop on board and live a unique cruise experience in Mykonos island. Sail to the ancient Delos, explore this UNESCO World Heritage site, swim in dazzling waters of Rhenia island and indulge in a freshly prepared meat and veggie BBQ on board.

What makes our product unique is the contact with sea & sun. Sailing away with Nadia K, you will have the opportunity to experience new adventures at the Aegean Sea and explore magical places at the Island of the Winds. Close your eyes, fill the sense of sun and wind, relax with the music and you’ll feel comfortable. Our visit to Unesco World Heritage site of Delos, is of great importance to get in touch and feel the pulse of Greek history and beauty! Then we reach the uninhabited island of Rhenia, where you can swim to crystal clear waters and explore the ocean bottom with the snorkeling gear , which is free for use onboard.

We setsail at 09:00am from Tourlos Marina. Our first stop is an hour away, the renowned Big Delos island. While there, you will have the opportunity to visit one of the most famous archaeological sites in Greek history : the birthplace of the Olympian God Apollo and the Olympian Goddess Artemis. You will have approximately one hour to explore the grounds of this significant cult center of Ancient Greece. Back on the boat, we will treat you to a traditional Mykonian lunch while you enjoy a drink of your choice, before sailing to the island of Rhenia. Rhenia is four times the size of its sacred sister Delos, and they are separated by a small channel. Rhenia is uninhabited and has four solitary sandy beaches (Glyfada, Stena, Lia and Ambelia) which rest in protected coves. Rhenia is a popular meeting point for yachts cruising the area due to its spectacular waters, which range in colour from a stunning emerald green to a beautiful turquoise blue.

• Cruise Duration: 5.00 Hours • Choice of a Morning or Sunset Cruise • Swim and snorkeling stop (Snorkeling Equipment Included) • Snap photos of the archaeological site of Delos & Rhenia • Fresh Main Meal served on Board • Drinks Wine, Soft drinks & traditional alcoholic Drinks (Bottled) • Free Transport from/to your Hotel

Experience the Joy of Sailing on a Yacht in a Friendly Small Group Atmosphere. Swim and Snorkel in Crystal Clear Waters, Indulge on Pristine Beaches of Uninhabited Rhenia Island. Explore the Magnificent Ancient Site of Delos Island and Savor a Buffet of Greek Delicacies

Explore Mykonos island with this 2to 4hrs private island tour. Discover hidden gems beyond the tourist hotspots and delve into the island's rich history. We will make several stops for photos and have some free time at Ano Mera Village. Pick up and drop off can be at your preferable place.

Pick up from the Cruise Ship Terminal and embark on an unforgettable journey through Mykonos with a local guide! Begin your Shore Excursion enjoying magnificent views of the Aegean Sea and nearby islands—perfect for capturing stunning photos. See some beautiful beaches & head to Mykonos Town, where you’ll stroll through narrow streets lined with charming whitewashed houses and explore famous landmarks like the Windmills and Little Venice. Along the way, your expert guide will share fascinating insights into the island’s rich history, culture, and hidden gems, giving you an authentic Mykonos experience. Whether you're seeking breathtaking views, fascinating stories, or simply a chance to immerse yourself in local life, this tour has it all. Don't miss out on the opportunity to discover Mykonos like a true local. Book your tour half-day sightseeing tour today and experience the island’s magic!

Welcome to the ultimate experience in Mykonos town - a delightful combination of a Walking Tour and a Tasting Tour, offering a sensory journey through the charming streets and delicious flavors of this captivating Greek island. Wander through the labyrinthine alleys of Mykonos town, where each step unveils fascinating tales of the island's history, culture, and architecture. Admire the enchanting white-washed buildings, vibrant bougainvillea, and the iconic windmills The tour will then lead you to a charming local bakery and authentic street food shops for the Tasting Tour part of the experience. Indulge your taste buds in a tantalizing array of Greek delicacies and traditional dishes. Traditional Greek street food offers a delectable variety of dishes bursting with Mediterranean flavors. The duration is approx 3h If you need a private pick up let us know so we can give you informations

In our classes, you’ll learn how to make classic Greek dishes like tzatziki, cheese pies, spinach pies, dolmades, and even how to masterize the world known greek gyros experience by preparing the gyros meat and baking your own pita-bread. It’s a hands-on experience that lets you bring the flavors of Greece into your own kitchen. With the guidance of our professional chefs you will learn not only how to cook these delightful dishes but deeply understanding the essence of Greek cuisine. This journey is about combining techniques, flavours, aromas and cooking tips to create meals that celebrate life, culture, and the joy of sharing. Our chefs will walk you through each recipe, imparting valuable tips and sharing stories that showcase the spirit of Greek hospitality. Join us for a memorable cooking experience. Whether you’re a beginner or already know your way around the kitchen, you’ll leave with new skills and a deeper appreciation for Greek cuisine.

Set off on an unforgettable journey through the captivating streets of Mykonos Town with a 2-hour walking tour. Perfect for travelers eager to dive into the spirit of this legendary Greek island, this experience invites you to savor the charm and beauty of its most iconic landmarks. Begin your adventure at the Old Port, pass by from Manto Mavrogenous Square and continue with the famous Mykonos Windmills, standing proudly as enduring symbols of the island’s rich heritage. Continue to the enchanting area of Little Venice, where colorful waterfront buildings seem to float at the edge of the sea. Finally, admire the architectural wonder of the Church of Panagia Paraportiani, one of the most photographed landmarks in Greece. Throughout the tour, your guide shares captivating stories and insights about Mykonos's everyday life.

A unique journey through the authentic side of Mykonos on powerful 450cc-600cc quad bikes!we have experience up to 10 years at this object.. Our team is ready to guide you through every corner with a fresh, authentic perspective.

Experience the island discovery with our bespoke private tour. The journey begins in the heart of Chora, where the romantic charm of Little Venice meets the iconic silhouette of the Windmills. We explore the sculptural beauty of Paraportiani Church and wander the chic, white-washed corridors of Matoyianni Street. Leaving the bustle behind, we head to the rugged Faros Armenistis for sweeping Aegean views before discovering the serene northern shores of Panormos, the untouched sands of Agios Sostis, and the wind-swept beauty of Ftelia. We then dive into the island’s authentic heritage at Ano Mera Village, visiting the historic Monastery to glimpse traditional life. The coastal adventure continues to the crystalline waters of Kalafatis and the cosmopolitan shores of Kalo Livadi. Finally, we conclude with a breathtaking Panoramic view of Mykonos town, capturing the white labyrinth against the deep blue harbor—a perfect finale to your personalized Greek escape.

Welcome to the enchanting Mykonos Town, where azure waters meet white-washed buildings and cobblestone streets. Mykonos Town is not only a visual masterpiece but also a culinary haven waiting to be explored. Join one of our signature walking tour as we wind through iconic landmarks and hidden alleys, uncovering local secrets and sampling the finest Greek delights Mykonos has to offer on an unforgettable Food Tour.

Discover the best of Mykonos with a customizable private tour designed for vacationers eager to experience the island like a local. In just a few hours, explore stunning beaches, hidden treasures, and iconic landmarks tailored to your preferences. Simply connect with your driver ahead of time to plan the perfect itinerary. Highlights of the tour include Agios Ioannis, the Faros Lighthouse, Panormos, Agios Sostis, Ftelia, Ano Mera village, the Monastery of Tourliani, and a picturesque photo stop at Kalafatis Beach. Highlights: • Capture breathtaking views and photos at Armentis Lighthouse. • Unwind on the sandy shores of Agios Ioannis Beach. • Stroll through the traditional village of Ano Mera and visit the historic Monastery of Tourliani. • Enjoy private pickup and drop-off in a comfortable air-conditioned vehicle.

Discover Mykonos like a local! This private sightseeing tour takes you beyond the usual spots to hidden gems, iconic landmarks, and stunning beaches—all with a knowledgeable local driver. •Perfect for couples, families, friends or strangers, looking for an intimate experience away from crowded tour buses. •(Optional)Sip Greek coffee in a hidden café, inside the famous alleys of Mykonos. •No rush, no stress,spend as much time as you like at each site, take in every detail, and enjoy the tour at your own rhythm •Visit famous spots like Little Venice & the Windmills •See the famous greek Chapelles from inside •Discover hidden gems tourists rarely see •Personalized experience based on your interests •Capture postcard-perfect moments away from the crowds. •Experience Mykonos through the eyes of a Mykonian. •Local Culture: Get insider tips on the best restaurants & nightlife. •Walk inside local neighborhoods •Hidden panoramic viewpoints •(Optional) Traditional meal on a Taverna

Join a shared group tour of Mykonos Island and Town. Get more out of your visit to Mykonos on a half-day tour led by a local guide. The island part of the tour is explored by vehicle (apox 2.5 hours), and the rest is a walking tour of Mykonos Town. Meeting location: NEW PORT – right at the Cruise Ship Terminal Gate.

It’s a very distinctive experience and one that will push the boundaries, delivering some resounding benefits and results every time. The commitment is to value and quality, and you will be heavily impressed with the results and the entire process in a professional way. During your tour at our facilities you will visit the olive grove, the winery, the wine press and for the end of the tour you will visit our traditional tavern.

This experience offers both; a relaxing beach time to enjoy pristine sands and crystal-clear waters of Aegean Sea, followed by free time in Mykonos Town, to self-explore the iconic streets, boutique shops, and cultural landmarks. Departures from: Tourlos New Port & Old Port Arrive at Elia Beach, known for its golden sands and crystal-clear waters. Enjoy approximately 3 hours of leisure time: Swim and relax on the beach. Explore the thrill of the island's most exciting watersports or indulge in beachside refreshments at a local taverna. Transfer to Old Port in Mykonos Town Arrive at Mykonos Town and start your own self-guided exploration (optional): See the iconic streets & landmarks; the Windmills, Little Venice & Paraportiani church. Return: Board the transportation for the return journey to the starting point Tourlos (New Port). Guests may choose to stay in Mykonos Town for further exploration and find their own way back to their Cruise Ship or Accommodation.

Combining 2 in 1, this tour is perfect for those visiting Mykonos as part of their cruise. Once you disembark, the local SeaBus welcomes and introduces you to the first coastal views of the picturesque Mykonos island. Soon, the torch is picked up by the Delos ferry, indicating the beggining of a once in a lifetime journey back in time with final destination: the island of Delos, the most famous and sacred of all islands in antiquity. A half-hour boat trip takes you to the historical Delos sanctuary, birthplace of Apollo and Artemis, Unesco's world heritage. Your guide shows you the ancient temples, mosaic floor villas, the Naxian Lions, the Roman amphitheater and more. This shared tour takes 5-hours overall and you are able to choose from one of two departure times when you book.

Let your taste buds do the traveling during this 6-hour cooking class in Mykonos. Make an authentic Greek meal and then savor it with your fellow cooks, all under the friendly and helpful eye of a professional. Learn how to make classics such as stuffed peppers and spinach pie, and wash it all down with wine and drinks. There is also the option to add a farm or island tour or a walking tour of Mykonos Town. Don’t miss this chance to learn about an important part of Greek culture and become a member of a true Mykonian family.

Swimwear party, next to the sea, in private beds-loungers, with champagne, dance rhythms, and incredible cocktails!! Want it? You got it! Visit two of the most famous beaches in Mykonos (Paradise & Super Paradise and have fun at the 4 best Beach Clubs in Mykonos : Tropicana, Paradise Beach Bar, Super Paradise Beach Bar & JackieO’

Explore Mykonos island with this 4hrs private island tour. Hidden beaches, famous attractions like Armenistis Lighthouse and Ano Mera Village and local places are some of the things you'll see with us. Our experienced guides and our luxury vehicles will make you feel comfortable and make this experience a time to remember! We will make several stops for photos and have some free time at Ano Mera Village for shopping and walking. Special requests can be accepted upon request and communication with the company in advance. The pick up and drop off can be at your preferable place free of charge.

Located in Ano Mera, in the heart of the island, the Mykonian Farm is the perfect choice to discover and to taste the finest Greek wines. Choose from a 12pm or 6pm departure time when you book, and you will not only learn the basic tasting techniques, but you will uncork and savor Greece’s most distinct blends.

Designed specifically for cruise passengers, this Mykonos shore excursion combines the island’s top highlights with smooth, stress-free logistics. Enjoy pickup directly from the cruise port and explore in comfort with a knowledgeable local guide who brings Mykonos to life through stories, history, and insider tips. Visit iconic landmarks like the Armenistis Lighthouse for panoramic views, the peaceful village of Ano Mera, before ending with a guided walk through Mykonos Town, including the famous Windmills, Little Venice, and Paraportiani Church. Carefully timed to match your ship’s schedule, this tour ensures a relaxed pace, well-organized stops, and a guaranteed return to port—so you can enjoy every moment with confidence. Ideal for first-time visitors who want to see it all without the stress.

This private tour is designed to give you a genuine experience of Mykonos through the eyes of a local. Instead of just visiting the famous sights, you will discover hidden corners, authentic villages, and beautiful beaches while learning about the island’s culture and everyday life. By the end of the tour, you won’t just feel like a visitor — you’ll feel a little like a local Mykonian yourself.

The suggested itinerary is carefully planned to introduce you to Mykonos by foot (in the pedestrian zone) and by car. You will see the highlights of the island and you will swim in the crystal clear water!

We will see the highlights of the island, we will tell you stories about them and visit the beautiful beaches accompanied with traditional homemade Greek and Mykonian snacks and drinks. Pick up is included from hotels and Cruise port. Shared Small group 8-people or Private.

Discover the island of Mykonos through this 4-hour tour (by car). Beaches, hidden destinations and famous sights are some of what you will enjoy during the tour. Τhe tour can be adjusted according to your needs and wishes, by contacting your driver in advance.Your driver will pick you up and drop you off at your preferred location. In this tour you will be able to see: • Agios Ioannis • The famous lighthouse of Mykonos ‘Faros’ ( stop for photos with the amazing view) • You will pass through the area of Panormos, Agios Sostis and Ftelia • A stop in Ano Mera, the traditional village of Mykonos and the Monastery of Tourliani • Stop for photos at famous beach of Kalafatis • You will pass through the beach of Kalo Livadi • The tour will end with a photo stop for a panoramic view of Mykonos