This one is a little morbid but still a remarkable sight. The Sedlec Ossuary (Czech: Kostnice v Sedlci) is a small Roman Catholic chapel, in which more than 40,000 skeletons are buried and used to "decorate" the chapel. Black death and wars took thousands of lives in the 14th and 15th century. A bout an hour train-ride outside of Prague if I remember correctly. Definitely worth a visit.
