The Orloj has been on the Old Town Hall since 1410, which makes it the oldest astronomical clock still in operation. Its main dial is not a clock face in the modern sense but a model of the sky, tracking the sun and moon through the zodiac and keeping Old Bohemian time, which counted the hours from sunset. The square below it has been the Old Town's centre for a thousand years — market, execution ground, parade route — and each century added its own house fronts without replacing the older ones: Gothic gables, Baroque facades and pastel Rococo stand side by side along the same terrace.
On the hour a crowd packs in under the tower for a mechanical performance that lasts under a minute: a skeleton tips an hourglass and pulls a rope, twelve apostles slide past two windows above, a cockerel crows. The twin black spires of the Týn church rise behind the houses on the eastern side, and the bronze figure of Jan Hus stands in the middle of the cobbles, placed there in 1915 on the five-hundredth anniversary of his burning.