Climb a steep hill in 90 seconds on the second-oldest urban subway in the world.

One of the newest mosques in a city filled with thousands.

An Art Nouveau gem hides beneath the layers of city grime obscuring this once-magnificent building.

Ancient serpentine sacrifice holder that has stood the test of time.

This remarkably well-preserved Egyptian plinth is pretty well traveled for a giant piece of stone.

A marvel of Byzantine engineering under the streets of Istanbul.

A small etching on the white marble parapet was written in runic script by a Viking mercenary.

Five sultans and their families rest in eternal splendor, teeming with overlooked beauty and drama.

1513 Turkish world map, full of European state secrets and snarky commentary.

No one is sure if the world's fourth-largest diamond had been found in a rubbish heap or was pawned by Napoleon's mom.

This column celebrates Rome's victory over the Goths, and may be the oldest Roman monument in Istanbul.

The ornate miniature mansions were built for Istanbul's feathered residents.

One of the best-preserved medieval streets in Europe.

A Turkish ghost town abandoned in a population exchange with Greece.

These tombs were built into the side of a mountain so that ancient angels could reach the dead.

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

This church houses the tomb—but not the remains—of St. Nicholas, the likely progenitor to Santa Claus.

A Lycian city of the dead carved into the hillside of Southern Turkey, complete with startlingly human touches.

Roman ruins, natural methane fires and a lovely beach.

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

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

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

The deepest underground city in Turkey was designed to protect 20,000 people behind massive stone doors.