The Prague Orloj on the southern wall of Old Town Hall has been ticking since 1410, making it the third-oldest astronomical clock in the world and the oldest still operating. Every hour, crowds gather to watch the procession of the Twelve Apostles in the upper windows, while the four flanking figures — Vanity, Greed, Death, and the Turk — animate below. The astronomical dial tracks the sun and moon through the zodiac; the calendar dial below was added in the 19th century.