The Olomouc astronomical clock forms part of the north wall of Olomouc City Hall. It was built in the fifteenth century and reconstructed several times thereafter. It is one of the few heliocentric clocks in the world, and there is a calendar at the bottom that dates national days and events such as the birthdays of Stalin and Gottwald, and therefore, this clock has become a distinctive tourist attraction that attracts visitors throughout the year.