Venice's "Island of the Mad."

Pompeii's less famous neighbor is still revealing her secrets.

The yawning maw of this pagan visage is said to bite off the hands of liars.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

Clap your hands at the base of the pyramid, and the song of a sacred Mayan bird will echo through the air.

Every equinox this Maya pyramid puts on a spooky ancient light show.

An abandoned village where the ruined foundations cling to a cliff.

Built in the 16th century, the tower is now in ruins.

A pair of stones embedded in an Edinburgh street memorialize one of the city's last public hangings.

Accessible only at low tide, the deserted island is dotted with World War II ruins.

A serene public space nestled within the remains of Glasgow’s Victorian maternity hospital

The fictional birthplace of the Chief Engineer aboard the Starship Enterprise.

It's said this was once the home of King James V's pet lion.

This pyramid is dedicated to all those who suffered martyrdom for civil and religious liberty in Scotland.

The main residence of the Erskine family and the hereditary keeper of the nearby royal Stirling Castle.

These formal gardens were designed to be admired from the vantage point of the castle.

A castle in the Scottish Highlands has been continuously inhabited since the 1300s.

The discovery of this Neolithic settlement, which contained a Stone Age "cathedral," threw archaeologists for a loop.

This tin chapel was built by POW's during World War II and is painted to look like something much more grand.

Enter the world under the hill at this ancient UK burial chamber.

This tiny island featuring 9th-century Viking ruins is only accessible at low tide.

Possibly the oldest of Britain's ancient henges is also one of its most stark.