Top 10 Cities for Urban Exploration

The Paris Catacombs feature legal opportunities for urban explorers. Rune Johansen/Photolibrary/Getty Images

Big draw: The Paris Catacombs

In the late 1700s, an outbreak of infectious disease was traced to a cemetery in Paris. To save the living, the dead were unearthed and moved to old quarries beneath the city [source: Catacombs Museum]. Those quarries are part of the subterranean network known as the Paris Catacombs.

Over several decades, every cemetery in Paris was emptied, the bodies relocated to the tunnels that would finally come to house about 6 million skeletons, stacked against the tunnel walls [source: Tancock].

The Catacombs are open to the public -- no breaking in required.

More to explore:

  • Fort du Portalet, Bearn: Built in the mid-1800s to defend against a Spanish invasion, converted to a German prison during the World War II occupation, liberated by Spain in 1944 and abandoned in the 1960s [source: Forbidden Places].
  • Ch√Ęteau Bijou, southern France: An abandoned castle (now protected as a historical monument) built in the mid-1700s and expanded in the early 1900s, noteworthy for its Italian-inspired architecture [source: Forbidden Places].

Next, over in Italy...