135 bronze medallions mark a French meridian line which once rivaled the hotshot Greenwich timeline.

A mud statue stands in the dark tunnels, seeming to hold up the weight of the city above.

Beggars were miraculously "cured" of their fake ailments when they returned home to this 17th century Paris slum each night.

Exquisite wall sculptures carved in secret by an early quarryman in an obscure corner of the Paris Catacombs.

A horde of stray cats rule in this secluded Parisian cemetery under a bridge.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

This massive library holds what was once the largest book collection in the world.

Abandoned railway line circling the city of Paris.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

A 16th-century fountain marks the site of a lost medieval cemetery once filled with mass graves.

Once the home of a hermetic monk, this cave now houses a small church.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

A series of caves under Castle Hill that once held the prisoner Vlad Tepes, better known as Count Dracula.

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

The only international border marker within the United States.