You heard of the two guys who recently opted in to a two-year, $1.5 million holiday? These are some of the sights they'll be privy to.Luxury website VeryFirstTo.com unveiled its £990,000 ($1.5 million) trip just a month ago, a luxury expedition to all 962 UNESCO World Heritage Sites in what's been billed as the world's most expensive vacation.Two men have reportedly signed up -- a Chinese student and an Italian businessman.Their "vacation" will take them from dazzling underwater ecosystems to the ruins of ancient civilizations, otherworldly natural landscapes to more modern works of architecture.Each year, around 25 sites deemed to have "outstanding universal value" are inscribed on the list, and we couldn't resist choosing a few favorites. We've rounded up 20 sites that we'd be looking forward to most if we were going on the trip.Angkor, Cambodia The site lies a 20-minute tuk-tuk ride from the city of Siem Reap, with the bulk of visitors traveling between November and February, when the weather is dry and temperatures are coolest (25-30 C). You can explore Cambodia on a Geckos Adventures tour.Acropolis, Greece It's possible to take a tour to the site, or simply wander there from Athens on foot. The route along Adrianou Street to the back entrance of the site is a gentler climb than the Dionysus Theatre entrance. For more information, visit the Greece tourism website.Bagan, Myanmar Located in Myanmar's central west, Bagan is serviced by flights, buses and trains from Yangon. Accommodation is centered in the surrounding villages of New Bagan and Nyaung Oo. Tours available with Intrepid.Galápagos Islands, Ecuador Located nearly 1,000 kilometers from mainland Ecuador, the islands are serviced by flights from Quito and Guayaquil. Multi-day boat cruises are generally the best way to explore the islands. Celebrity Cruises will get you around the Galápagos in style.Göreme National Park and the Rock Sites of Cappadocia, Turkey Due to the remote nature of the site in central Anatolia, most visitors opt to fly in from Istanbul to visit the area on a tour, or drive. Hotels cut out of the rock provide accommodation. For more information, visit the Turkey tourism website.Great Barrier Reef, Australia Larger islands are well-serviced by flights from mainland Australia. It's also possible to visit the reef via day trips from northern Queensland ports including Cairns and Port Douglas. For more information, visit the Tropical North Queensland Tourism website.Hampi, India Hampi is serviced by overnight bus from Goa. Trains run to nearby Hospet from Chennai, Mumbai, Bangalore, Delhi and Calcutta, and visitors will find a good range of low- to mid-range lodgings around Hampi village. Tours available through On The Go Tours.Iguazu National Park, Brazil and Argentina The less-developed but refreshingly uncrowded Brazilian side of the falls is a half-hour bus ride from the city of Foz do Iguaçu. It's the same distance to the falls from Puerto Iguazu on the Argentine side. The two countries are connected via a bridge downriver of the falls. For more information, visit the Argentina tourism website.Los Glaciares National Park, Argentina Most visitors to this remote southern region of Argentina base themselves in El Calafate, the closest town to the park entrance. There are daily flights and buses from the capital Buenos Aires. For excursion options, check out Gigantes Patagones.Machu Picchu, Peru Several multi-day treks terminate at Machu Picchu, but it's also possible to take a train from Cusco to Aguas Calientes, and climb a steep flight of stairs or bus up to the site. Only the first 400 daily visitors are granted entry to Wayna Picchu, a separate set of ruins overlooking the main complex. Tucan Travel offers a range of tour options.Mont-Saint-Michel, France Mont-Saint-Michel is serviced by buses/tours from Rennes and Saint-Malo, but it's also possible to lodge in one of Mont-Saint-Michel's small hotels. For more information, visit the Normandy tourism website.Petra, Jordan Buses and day/overnight tours run from Jordan's capital Amman and the port city of Aqaba. It's also possible to organize tours from Egypt, and the Israeli resort town of Eilat. For longer stays, bunk down in Wadi Musa, Petra's neighboring town. For more information, visit the Jordan tourism website.Pyramids of Giza, Egypt Just 25 kilometers southwest of Cairo along the Nile River, the complex is most easily visited on a day trip from Egypt's capital. For more information, visit the Egypt tourism website.Rapa Nui, Chile While it's possible to access Easter Island by air from Tahiti, most visitors opt for the five-and-a-half hour flight from Santiago, Chile. For more information, visit the Chile tourism website.Serengeti National Park, Tanzania The short October/November and March/April rainy seasons notwithstanding, the Serengeti, usually accessed via Kilimanjaro or Nairobi airports, offers great game viewing year-round. For tours, visit the Audley Travel website.Sigiriya, Sri Lanka The central Sri Lankan site is located two to three hours by local bus from the city of Kandy (via Dambulla, home to a massive cave temple complex). It's also possible to organize a tour or personal driver from Kandy. For more information, visit the Sri Lanka tourism website.Tulum, Mexico Located a few minutes drive from the small Yucatan Peninsula township of Tulum, the easily accessible ruins lie about 60 kilometers south of the larger township of Playa del Carmen, and a further 60 kilometers from Cancun. For more information, visit the Mexico tourism website.Valletta, Malta Just south of Sicily, Malta is connected by flights from across Europe. It's possible to lodge in Valletta, but the bulk of visitors make for the tiny nation's beach resorts. For more information, visit the Malta tourism website.Venice and its lagoon, Italy Venice is served by nearby Marco Polo and Treviso airports, while trains arrive at the Venezia Santa Lucia train station in the western part of the city. For more information, visit the Italy tourism website.Yellowstone National Park, United States Located around 100 kilometers from Jackson Hole, Wyoming, the closest major airport hub, the park has five main access points. Most visitors choose to drive throughout the park, camping en route. For more information, visit the Wyoming tourism website.