One of several skulls claiming to belong to the beheaded St. John the Baptist is on display at this Roman church.

An alchemist's "magic door" stands in the middle of a Roman park.

A submerged archeological park still holds the wonders of a Roman Sodom.

While only two of the ancient buildings at this site are actually churches this was one of the earliest Irish pilgrimage sites ever.

The ruins of an 800-year-old monastery boasts the tallest round tower in Ireland.

Catacombs turned marketplace.

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

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

The site of London's first coffee house has been serving refreshments of one kind or another for 360 years.

A closed London rail station created to cart away the dead still bears the marks of attempts to make it less morbid.

A hands-off space for graffiti artists to hone and display their skills.

An unusual round church in London with a Templar past.

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

A tree-like building perches on its trunk in the Steglitz neighborhood of Berlin.

This futuristic German spa allows visitors to float in a pool of salt water while zoning out to underwater techno.

The very center of Paris is surrounded by a bevy of strange good luck rituals.

The bunker where Hitler took his own life is hidden under this deliberately ordinary parking lot.

This massive, ancient stone was disassembled and then put back together again.

One of the Seven Wonders of the Modern World holds the world's tallest metal staircase.

This "Palace of Purification" has made many film appearances as a dark and sinister headquarters.

This abandoned seaside fortress is now simply an imposing ruin being taken back by nature.

A crumbling hospital from the 1850s on Roosevelt Island.

An enormous, inside-out glass globe built in 1935.

An abandoned stretch of highway, deteriorating next to the operational one.