The Astronomical Clock of the Old Town or the Astronomical Clock of Prague is a medieval astronomical clock mounted on the southern wall of the Old Town Hall in Prague. The dominant feature of the clock is an astronomical dial situated in the middle and a calendar board underneath. The astronomical dial derived from the astrolabe can be used for reading various times, astronomic cycles, the position of the Sun and which zodiac constellation it is just going through, the position of the Moon above or under the horizon, its phase and position towards the Sun. The calendar board can be used for reading the current month, day and fixed Church holidays. Above the astronomic dial there are two windows in which the apostles move. The astronomical clock is completed with statues by its sides, a bust of an angel between the apostles’ windows and a cock fit with a sound system in the upper part above the windows. The Astronomical Clock of the Old Town is probably the best-preserved medieval astronomical clock in the world. It is one of the most popular tourist destinations of Prague and a part of the historic centre, which is listed in the UNESCO cultural sights list.