Sigiriya, Sri Lanka — The Ancient Rock Fortress in the Sky

In 477 AD, Prince Kashyapa seized the throne from his father, King Dhatusena, and — fearing revenge from his half-brother Moggallana, the rightful heir — retreated to this near-vertical granite outcrop in the middle of the jungle and built a fortified royal city on its summit. For eighteen years Sigiriya was the capital of Sri Lanka: a palace ringed by moats and ramparts, with landscaped water gardens at its base and a private staircase rising through the paws of a colossal brick-and-plaster lion. When Moggallana finally returned with an army in 495 AD, Kashyapa was defeated, and the city was abandoned. Buddhist monks used the surrounding caves as a monastery for centuries afterward, before the site was largely forgotten until a British army officer, Major Jonathan Forbes, rediscovered it in 1831. Today, Sigiriya is recognised by UNESCO as a World Heritage Site (inscribed 1982) and remains Sri Lanka’s single most-visited archaeological site — a rare case of a 5th-century city where the engineering, gardens and art all still survive largely intact.