Hidden beneath the famous St. Peter's Basilica is a veritable city of the dead that may hold the remains of St. Peter himself.

An incarceration museum on the spot of possibly the oldest prison in England.

A makeshift shrine to the late rock star is still kept up on the nondescript façade outside 1 Logan Place.

Catacombs turned marketplace.

One part local history, 99 parts gruesome haunted house.

This London pub hides a peculiar secret: a recreation of the rooms shared at 221b Baker Street by Sherlock Holmes and Dr. Watson.

Banksy gives themself artistic license with this piece of London street art.

The popularity of Sherlock Holmes led to the creation of his fictional address, turning the orderly London street numbers askew.

A new sculpture calls attention to climate change in the centuries-old city it threatens.

Go inside to really appreciate this 500-year-old technological masterpiece.

This palatial spiral staircase was so unusual the name "snail" was given to the noble family who built it.

This Venice bookstore has resigned itself to constant flooding by keeping its books in bathtubs and boats.

A local student's chance encounter with Keith Haring led to the creation of one of Europe's largest murals.

Designed by Horace Trumbauer in 1893, this Gothic-style castle is now a home for academics.

Built on the foundations of an ancient Roman villa, the unique architecture of this castle on the Catalan coast was used as a set for 'Game of Thrones.'

Kings Cross Station pays tribute to its role in Britain's best-selling book series.

One of the greatest movie directors of all time lived and worked in this London flat from 1926 to 1939.

In Twickenham sits a small whitewashed castle that inspired Mary Shelley's 'Frankenstein.'

Last residence of H.P. Lovecraft featured in his story "The Haunter of the Dark."

Originally envisioned by King Ludwig II to rival Versailles, Herrenchiemsee's "New Palace" remains half-gilded for lack of funds.

The prison where Hitler wrote "Mein Kampf," and 278 Nazis were later executed for war crimes.

This German version of Universal Studios holds a vault of treasures from the NeverEnding Story.

A stairway to heaven, or to nowhere at all.

A fearsome dragon clings to a corner of Munich's city hall.