An alleyway plaque is all that remains of the independent Texas' envoy that forgot to pay their rent for over a century.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.

The perfectly preserved underground rooms where Churchill plotted the war against Germany.

The atmospheric road was never meant to be so creepy.

A 300-year-old tea shop that brought tea to the English people, not to mention the Queen herself.

One of the few remaining casualties of the London Blitz, this destroyed church has become an enchanting public garden.

The sign at the garden gate reads: "These Plants Can Kill."

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

A tour of underground Berlin takes you through WWII air raid shelters and tunnels used to smuggle people out of East Germany.

Golden cobblestones remember a time when this small alley was used to avoid having to give a Nazi salute.

These bronze pamphlets remember a remarkable group of Germans who fearlessly opposed the Nazis in the very center of their power.

A preserved Nazi labor camp now has a Holocaust museum on site and memorials to the thousands that died while imprisoned at the camp.

This jaw-dropping 19th-century bridge uses its reflection to form what appears to be a perfect circle.

A rare example of World War I trenches from the British front.