The Tower of the Winds or the Clock of Andronicus Kirrest is a small octagonal building made of Pentelian marble of the 1st century BC. It is located in the Roman Agora. The hydraulic clock is powered by a spring in the rock of the Acropolis. The direction of the wind was indicated by an iron weather vane mounted on top of a pyramidal roof. The facade of the tower is decorated with reliefs depicting 8 winds with symbols. During the Christian period, the building was turned into a church, and in 1750 into an Ottoman prayer house.