This famous city eluded concrete detection until the early 2000's.

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

A marvel of Byzantine engineering under the streets of Istanbul.

Two geological phenomena in one precarious locale: a towering stone window, and a deep blue void.

This church is named for one of the most dramatic tales in the early Christian church.

At more than 5,000 years old, these structures are among the oldest free-standing stone buildings in the world.

These temples are among the oldest free-standing stone buildings in the world.

Ancient mysterious ruts carved in the bedrock.

Enigmatic tombs and cave dwellings on the outskirts of a rural village.

Overshadowed by other, more famous Maltese catacombs, this ancient burial chamber has one of the best examples of a ritual agape table.

The fishing boats that moor in this small lagoon enter and leave through a tunnel to the sea.

This spectacular dome managed to survive after being bombed in World War II, in an event known as the "Miracle of Mosta."

This prison on the Maltese island of Gozo is almost 500 years old, and they have the graffiti to prove it.

The floor of this spectacular Baroque sanctuary is covered in memento mori.

This subterranean necropolis holds three floors of antler-dug grave caves.

Burial grounds for more than 1,000 bodies deep under the modern town of Rabat.

Stone Age solar temple is aligned with the sun on each equinox and solstice.

One of the two original gateways into the Kasbah, this gateway is a nesting site for storks.

The ruins of an early-18th-century complex that could once house up to 12,000 horses.

The world's largest concentrated solar power plant.

The designated Jewish quarter in Fez dates back to the 15th century.

Exploring the wilder, more passionate sibling of Erg Chebbi feels like discovering a secret sun-kissed planet from another galaxy.

The courtyard of this small Marinid madrasa is a dazzling example of intricate Islamic architecture.

This vast masterpiece of Moroccan architecture spreads across 20 acres.