THE REMOUCHAMPS CAVES, BELGIUM
These caves contain the longest subterranean river known in the world, the Rubicon (not to be confused with the Rubicon in Italy). The caves opened in 1912 and were originally equipped with torches. 8,000 years ago Paleolithic hunters sheltered themselves in the caves; much later the same area was used as a wine shelter. More recently the caves were used as a shelter during World War II.