Hidden beneath the waters of Lake Michigan rests a perfectly intact ship from the early 1900s.

This enormous World War II relic is one of the largest wooden structures in the world.

Twelve hundred stone carvings guard this off-the-beaten-path Buddhist temple.

Nineteen ancient rock-cut Buddhist caves can be found on the outskirts of Mumbai.

This ancient hydrological marvel is now the base of a modern outdoor cinema.

A World War II torpedo launch station abandoned off the Polish coast.

This historic little railroad runs through some of the most beautiful scenery in Germany.

A haunting theme park is slowly being swallowed by the jungle.

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

One of the most well-preserved temples of ancient Egypt.

The abandoned ruins of a beautiful medieval castle just outside Barcelona.

Cretean quarry suggests real-life site for ancient Greek myth of the man-eating Minotaur in his labyrinth.

A futuristic hovertrain is parked unceremoniously alongside a nondescript road.

A cave network located at the southernmost tip of mainland Greece was once believed to be an entrance to Hades.

This magnificent stepwell is designed as an inverted temple and adorned with 1,500 sculptures.

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

A centuries-old complex of hand-dug stone chambers has sheltered locals in times of trouble.

A 1,500-year-old, 3-story subterranean city where ancient Persians took refuge in times of war.

Meant to be one of the most extravagant hotels in the world, now an eerie, abandoned architectural gem in Mexico City.

Stunning ruins of what was once the center of one of the greatest empires in East Africa.

The construction of a tram line unveiled hidden remnants of the old medieval city.

This 14th century castle withstood years of battle but is now sliding off the hills into the Danube.

A subterranean shelter remains intact under a busy Paris railway station.

A 70-foot-deep ice cave formed by lava from Mt. Fuji on the edge of Japan's "Suicide Forest."