This cluster of little wooden huts once ground local farmers’ wheat into flour during the days of the Austro-Hungarian Empire.

There's a mini version of Iguazu Falls hidden in the Balkans, and it's got a rope swing.

This historic timepiece is thought to be the only public clock in the world that keeps lunar time.

This ironic war memorial thumbs its nose at a campaign of inedible humanitarian aid food products.

Some of the best-preserved specimens of the monumental medieval tombstones found throughout Bosnia and Herzegovina.

This historic cemetery was inaccessible for several years due to dozens of land mines.

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

This Budapest bar allows drinkers to leave their mark on the walls, floor, and even ceiling.

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.

A historic house left in "dramatic still life."

The signs of a long buried road can still be found hidden beneath a London sewer grate.

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

Winding paths and ramshackle mausoleums in the oldest "park cemetery" in London.

The largest of London's subterranean rivers and once a mad, bad center of London life.

An eccentric 18th century naval officer built a ship's quarterdeck on his roof, the inspiration for Mary Poppins's "Admiral Boom."

The grounds of this Jacobean estate contain one of the oldest mulberry trees in England.

The alleged birthplace of Lady Jane Grey, who was executed at age 16 for claiming the throne of England.

The remains of the oldest synagogue in Britain lay forgotten for seven centuries, hidden under a humble shop.

An abandoned set from the 1980 film "Popeye," claimed and repurposed as a theme park by creative locals.

The eclectic seaside sanctuary caters to a rather fowl crowd.

The beautiful tunnel that ran from the lobby to Penn Station is still hidden underneath 34th Street.

The world's oldest surviving music hall was also once a freakshow.

A South African bar inside a hollowed out 6,000-year-old Baobab.