This coffee shop lies hidden beneath a historic church.

Rebuilt remains of a temple to Roman god Mithras.

A 2000-year-old Roman amphitheater lies just below Guildhall Yard.

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

A "sinister, whimsical, tacky, and really orange" public art installation hidden under a Seattle bridge.

A nun spent 16 years painting the stunning Celtic mural that covers the interior of this WWI memorial.

The comedy and tragedy of Oscar Wilde is preserved in a Dublin park, captured in a sculpture of colorful stone.

The enchanting archway is the only surviving portal into Dublin's lost medieval wall.

Not quite the menace it once was, this monster still has some chops.

Climb inside an iron crystal magnified 165 billion times its normal size.

Meet the bronze beloved pet to a family of famous peeing statues.

A fantastical 13th-century fortification sandwiched by a modern hotel in central Brussels.

A century-old hotspot for jazz, frequented by everyone from Charlie Chaplin to Al Capone.

An enormous park-like oasis, full of famous Chicagoans' graves.

These abandoned grain silos and tunnels are an urban exploration dream.

This art gallery and oddities boutique bewitches visitors with a trove of occult trinkets and eccentric antiques, work by an ever-changing roster of underground artists, and classes in tarot and other mystic arts.

How did a 2,000-year-old Roman column find its way to a Chicago park?

A monument to the art of slicing people open.

A journey begins with a single step, and for many, the road-trip of a lifetime started at this Chicago intersection.

This alley in downtown Chicago held the bodies of over 600 people after the fateful Iroquois Theatre fire.

According to legend it was a nap taken under this tree that kicked off the California Gold Rush.

This massive Brazilian church is built like an angular, technicolor pyramid left by Mayans from the future.

Da Vinci's equestrian statue, 500 years in the making.

This Italian stadium makes liberal use of fascist statuary to evoke classical sporting arenas.