Brno is the biggest city in the eastern part of the Czech Republic and the second-largest city in the country. It was once called Brünn, when the area was still part of the Austro-Hungarian Empire. It is famous for numerous caves, but actually they are located in a small karst area to the north of the city. The city has a lot of subterranea, from a museum of prehistoric man with cave replicas with paintings, to an ossuary. There are air raid shelters, atomic bunkers, historic cellars, and abandoned cisterns.