The medieval astronomical clock stands on the southern wall of Old Town Hall, its blue and gold face tracking sun and moon across a mechanical cosmos. Every hour between 8 a.m. and 11 p.m., twelve apostle figures process past narrow windows while a skeleton strikes the time. The mechanism is part astrolabe, part primitive planetarium—showing the universe's current orientation relative to Earth.
The mechanical clock and astronomical dial date to 1410, created by horologist Mikuláš of Kadaň and Charles University mathematics professor Jan Šindel; the first recorded mention appears on 9 October 1410. The calendar dial was added around 1490. During the Prague Uprising in May 1945, Nazi shelling damaged the clock; wooden apostle sculptures burned. The machinery was repaired and the clock resumed operation in 1948.
You stand in Old Town Square watching the golden sun icon move along the zodiac ring. The blue circle at center represents standing Earth; above it, the sky you can see. Red and black zones mark what lies below the horizon. Three overlapping time scales—Roman numerals for Central European Time, curved golden lines for medieval unequal hours, Schwabacher numerals for Old Czech Time—turn this single face into a chronicle of how humans have measured the day.