Astronomical Tower in Clementinum Prague, Baroque astronomical tower in Old Town, Prague, Czech Republic
The Astronomical Tower of Clementinum is a baroque tower with a white facade rising above the complex in Prague's Old Town. It has multiple observation chambers and houses original astronomical instruments from the 18th century.
The tower was built in 1722 as a center for astronomical research, when Prague's scientific work was gaining importance across Europe. Over the centuries, it remained a key place for observing and recording celestial movements.
From the tower's gallery a flag signalled noon from 20 July 1842, on the initiative of Count Karel Chotek, so Prague's clocks could be set. The flag was red and white in the Bohemian colours, black and yellow under director Weinek (1883–1913), and red and white again after 1918. From 1891 to 1926 a cannon shot from the bastion of St Mary Magdalene on Prague Castle followed the signal in good visibility.
The viewing gallery sits 52 m up and is reached by 172 steps, so allow time for the climb. A small exhibition inside the tower displays historical astronomical, geophysical and meteorological instruments. The tower is visited on guided tours of the Clementinum complex.
The noon signal was given from the tower from 20 July 1842 by waving a flag, so Prague residents could set their clocks. From 1891 to 1926 a cannon shot from the bastion of St Mary Magdalene at Prague Castle followed when visibility was good. The last flag signal was given on 31 January 1928.
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