Water

Crumbling ruins of the thermal baths that once attracted royals and aristocrats from throughout Europe.

Abandoned tunnels dug for the once-thriving sea salt industry on the coast of southern Spain.

The Pentagon sits on a former island that was in Virginia at low tide and D.C. at high tide.

The subterranean "lake" below the Paris opera house inspired the Phantom of the Opera's lair.

One of the world's largest tanks mimics the experience of watching rare whale sharks, giant rays, and deep sea creatures from the ocean floor.

Nature's slip and slide.

A wrecked ship dating back to the American Revolution was only recently discovered off the Delaware coast.

Medieval irrigation channels built into the sides of mountains provided Valais with water for hundreds of years.

A Nessie-like monster supposedly lurks in this lake.

An impressive display of ships and artifacts from the ancient Mediterranean maritime trade.

A water pumping station disguised as a residential home to assuage concerned neighbors now tricks most passersby.