Ecuador's largest Incan ruins show evidence of sophisticated irrigation and diplomacy among the ancient builders.

This legendary city has been a tourist attraction for centuries.

Even France's favorite aquatic son Jacques Cousteau, couldn't get to the bottom of it.

A cave dwelling that was started by the Celts, expanded by monks, and finished by knights.

Abandoned city hidden from the world by tropical forest and isolation on the coast of Kenya.

The enigmatic and seldom visited ruins of a Mayan city-state.

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

The stones of this Incan wall complex fit together so well you couldn't fit a piece of paper between some of them.

Between Neo-Pagans and Neo-Nazis, these strange rock formations have a curious cult following and a very strange history.

Stone age urban planning.

Mausoleum and Holy Seat of Antiochus I of Commagene.

A sacred lake with thousands of sacred carp and a biblical history.

This hunter-gatherer architecture is believed to be the oldest religious complex known.

The largest prehistoric ruins south of the Sahara, once a powerful center of international trade.

The second-largest ceremonial mound in the United States is an artificial hill that is loosely shaped like a pentagon.

One of the oldest trees in Britain may have been witness to some of the country's formative moments.

The giant figure on the back of this turtle-shaped temple actually hides a memorial pendulum.

Ozymandias’ time-keeping temple.

One of the most popular megalithic sites in Ireland stands as a humbler version of Stonehenge.

Preserved Inca city and site of the last Inca stronghold against the Spanish conquistadors.

This natural Icelandic fissure allows divers to swim right between two volatile tectonic plates.

An Icelandic island full of diving birds and legend.