There are two major sights in Prague which attract most of the tourists coming there: the skyline of the Castle and Charles Bridge and the Astronomical Clock. Whar is so special about the latter? Well, it is the only medieval orloy in the world which is still in operation. Second, it is the atmosphere and appearance of the whole Old Town Square which brings you back in time to the medieval times. The Clock itself is integrated into the southern facade of the Old Town Hall tower. It occupies three floors of the tower. Ground floor bears the Calendar Dial, structure of twelve frescoes representing the twelve months of the year. First floor is the home of the Astronomical Dial, the actual clock showing four kinds of time in one dial. Second floor has the balcony with windows where parade of the Twelve Apostles shows each hour. The original mechanical clock engine powering all moving parts of the whole orloy is spread over all three floors of the tower. What does the clock do, except showing time? Well, it shows four kinds of time: Babylonian, Siderian, Old Medieval and local Central European time, all in one dial. Then it shows the presentation of animated figures around and above the dial at each full hour. Once the tower bell begins to chime, the Death tolls her small bell and windows above the dial get opened. Parade of the Twelve Apostles proceeds beneath from left to right. The Apostles are wooden figures. Each makes appearance in both windows and then disappears. The windows close up after the last Apostle. Thats it. The beauty of this all is the fact that the mechanism was put into operation long before Christoph Columbus set off on his sail to rediscover America... This is probably why the Clock attracts so many tourists who stand in the crowd in front of the Old Town Hall tower, waiting for the bell to chime. And why the Prague Astronomical Clock replica has become one of the most popular souvenirs people buy in Prague and bring home.