A shining sculpture made of 3,115 lights, the number of visible stars in the Northern Hemisphere.

A century-old network of freight tunnels underneath the city's historic business district.

The twin towers in this Chicago fountain use 50 foot tall video screens to spit on people.

An underground city of salt.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

A magical sinkhole on the Yucatán Peninsula is adorned with mini waterfalls and hanging vines.

Hidden beneath the streets of London is a secret subway that only carried mail.

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

A breathtaking bridge that crosses a vast gorge over a river's torrents, and has a tale of a devil architect attached.

The world's longest and deepest train tunnel.

The bizarre visions of H.R. Giger, tucked away in a Swiss medieval city.

The alpine falls where Sherlock Holmes apparently met his demise can actually be visited.

This memorial commemorating fallen Swiss Guards of the French Revolution has been called the saddest stone in the world.

What was once a unique system of urban elevators is turning into a mechanical ruin.

Astonishing rock formations dot the Brimham Moor landscape.

The National Railway Museum in York is the largest railway museum in the world, attracting almost 1 million visitors per year.

To literally keep their waste out of their own backyards, the citizens of this English city built an impressive sewer system that is still in use today.

This bridge is the first to be made entirely from iron, but designed like it was still made of wood.

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

Legends say that this Art Deco apartment building almost became Hitler's British headquarters.

The handiwork of a underdog clockmaker who solved an impossible problem for an Empire, and forever revolutionized seafaring.

This former medical factory gives home to cutting edge arts in the shadow of a gas works.

You'd never know the houses at 23-24 Leinster Gardens were fakes—until you see the train tracks on the other side.

The first tunnel to be dug beneath a river, repurposed as an art and museum space.