Forgotten and then destroyed by fire, this was once one of the largest saltwater swimming pools in the world.

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

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

The world's largest wooden structure.

The final resting place of the great navigator, or maybe his brother.

Claiming to be the oldest hat store in the world, this historic haberdashery had a hand (and a head) in the creation of the Bowler.

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

Terrifically morbid cemetary and site of famous Paracelsus' grave.

Two stunning 17th-century libraries and a cabinet of curiosities.

Synagogue built from the stones of Solomon's temple contains the golem of Prague.

Macabre astrological automaton clock dating to the late 1400s.

Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.

Despite attempts by local police to discourage it, Beatles-inspired graffiti has been a means for artists to air grievances for decades.

Museum dedicated to the terror regimes of Hungary.

Uh, pardon me, ma'am, but I couldn't help noticing that there's a Columbo statue in the middle of Budapest.

The mummified right fist of a 1,000-year-old saint-king sits inside an ornate golden reliquary.

Budapest's Communist-era statues, banished to the suburbs.

In this historic region, homes and churches are carved into ancient volcanic rock formations.

While not Turkey's deepest underground city, this subterranean redoubt is the largest.

A dwindling menagerie of anthropomorphic oil derrick animals still dot the barren California landscape.