Prague Castle, Czech Republic

Prague Castle is the largest ancient castle complex in the world at 70,000 square metres, dominating the Czech capital since the 9th century and now serving as the official residence of the Czech president. The complex includes St Vitus Cathedral (begun 1344), the Old Royal Palace, the Basilica of St George, and Golden Lane. UNESCO listed it as a World Heritage Site in 1992. It receives over 3 million visitors annually — 36% more than Neuschwanstein and 1 million more than Edinburgh Castle — and its cathedral's stained glass windows are 400 years newer than those in St Vitus's original chapel.