Medicinal spa created with the discharge from a geothermal energy plant.

This beach runway is off limits during high tide.

A magnificent, iconic stone tower in the Scottish Highlands.

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

Thanks to both terrific preservation and historic vandalism this ancient site is known as the "Heart of Neolithic Orkney."

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

This Scottish burial tomb once held hundreds of ancient eagle bones.

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

A red sandstone freestanding monolith rises out of the sea in northern Scotland.

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

The true age of this ancient stone circle is unknown, but its stunning vista isn't in question.

Carvings in Turkey's Marble Road may have directed ancient Romans to a hidden brothel.

The ancient latrines of the Greeks, in all their public glory.

Roman ruins, natural methane fires and a lovely beach.

While not Turkey's deepest underground city, this subterranean redoubt is the largest.

Roman ruins top white travertine terraces formed by ancient hot springs.

In this historic region, homes and churches are carved into ancient volcanic rock formations.

Charnel house at the foot of Mount Sinai.

These Egyptian statues have survived for 3,400 years and were an acoustic wonder of the ancient world.

The deadliest diving spot in the world is also a stunning geological marvel.

One of its engravings is believed to be among the first representations of medical and surgical instruments.

Ancient Egyptian relief, claimed to depict an electrical light.

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

The massive cave church of Cairo's Zabbaleen community is one of the largest Christian churches in the Middle East.