If you ever visit Prague it is an absolute "must" to visit the Jewish Quarter with its synagogues, the Old Jewish Cemetery, and its streets, many lined with wonderful Art Nouveau buildings.
One of the most interesting places is the Old Jewish Cemetery. It was founded in 1478 and was for over 300 years the only burial ground permitted to jews. Because of the lack of space people had to be buried on top of each other, up to 12 layers deep. Today we can see over 12,000 gravestones crammed into the tiny space, but several times that number are thought to have been buried here. The last burial was in 1787. (source: Travel guide Prague, DK Eyewitness Travel).