The often-rebuilt Prague Castle has overlooked the city since the 9th century. Over the next few hundred years came the churches, houses and palaces of Old Town, the synagogues and cemetery of the Jewish Quarter and majestic Charles Bridge, which spans the Vitava River. Today, the bridge's pedestrians watch musicians, artists and fire eaters. Other can't-miss attractions include the Museum of Communism, Old Town's astronomical clock and the Estates Theater, where Mozart conducted Don Giovanni.