The narrowest street in Paris.

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

A flock of peculiar-colored sheep graze in this small Swedish town.

Said to be one of Sweden's most haunted places, this vicarage once even attracted a ghost-busting priest.

More sculpture than building, this architecturally significant temple was built on the spot of Saint Peter's crucifixion.

This private skyway is filled with art and was expanded explicitly so that Hitler could appreciate a river.

The plague quarantine island home to the alleged "Vampire of Venice."

A collection of objects supposedly singed by the hands of souls in purgatory.

Hidden in an Italian forest is a completely homemade amusement park that has taken a lifetime to create.

Venice's "Island of the Mad."

The final resting place of the poets Shelley and Keats.

An ossuary built in 1210 to collect bones from the Ospedale Maggiore of Milan.

The doodles of a genius line the walls of a secret room under the Medici Chapel, where they were hidden for nearly 500 years.

The ruins of this long-abandoned unsuccessful gold mine can still be found.

This stately structure has been abandoned for half a century.

The stone walls of a home built to withstand a California wildfire still stand after more than a century.

The Swiss artist's bulbous and overgrown shape-shifting sculpture controversially graces the center of Bern.

For centuries no one knew there were hundreds of bones and precious artwork hidden beneath this Swiss church.

The steepest classic funicular in the world glides along a dizzying incline.