The Prague Astronomical Clock, known as the Orloj, is mounted on the Old Town Hall in Prague’s Old Town Square and is the world’s oldest astronomical clock still in operation, with its mechanical clock and astronomical dial dating to 1410, created by horologist Mikulas of Kadan and astronomy professor Jan Sindel.
A calendar dial was added around 1490 and gothic sculptures decorated the facade, followed by wooden statues in the 17th century and figures of the Apostles after major repairs between 1787 and 1791; the clock suffered heavy damage during the 1945 Prague uprising but was later restored. A popular, though historically unconfirmed, legend claims the clockmaker Hanus was blinded so he could never build another like it.
Every hour from 9 AM to 11 PM, two windows open to reveal twelve “walking” apostles in a short mechanical show; viewing the clock is free with no booking required, and most visitors spend just 15 to 30 minutes watching the display before exploring the surrounding square.
