An Aztec snake god has taken the material form of an apartment complex.

Eat your Big Mac in a DC-3.

One of the famous Czech artist's lesser-known Prague installations appears to be a glowing fetus affixed to a drainpipe.

An Orwellian sculpture with eyeball cameras watches passersby.

A church of bones, decorated with 40,000 human skeletons.

A nearly unconquerable island-fort in the Indian Ocean.

At this museum in Iceland, visitors can sample fermented Greenland shark.

A moody and picturesque riverside ruin overgrown with vegetation.

Only 68 people per day are allowed to visit this New Zealand bird-watcher’s paradise.

The medieval network of canals hidden underneath the city is opened to explorers each year.

Near Birmingham, England three and a half miles of top-secret tunnels housed a World War II “shadow factory” and a Cold War nuclear bunker.

A well-preserved network of cavernous tunnels have spent silent centuries removing Toronto's waste.

A medieval military street hidden beneath a charming French fishing village.

Some locals believe the fabled lost gold of General Yamashida is hiding somewhere beneath the city.

Dug as a secret royal escape route, the tunnel became a wartime bomb shelter and dumping ground for vintage cars.

A hidden tunnel leads to a medieval queen's shrine buried beneath a parking lot.

This abandoned subway station beneath the Waldorf-Astoria hotel is allegedly used to secretly transport presidents.

A network of concealed passageways lies within a busy London Underground station.

Walking by this fence is like strolling along a portal to various fictional worlds.

Hidden in a grotto 26 feet below Nottingham's oldest hotel, this stylish subterranean drinking den is notoriously hard to find.

A 32-acre fun park dedicated to all things cheese.

Large, airy hallways hide within an impenetrable fortress that beckons urban explorers.

This quaint Italian town keeps losing ground as the sides of its plateau slowly erode.

A fairytale island floats in the middle of Italy's little-known Lake Orta.