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

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

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

Once described as the "Eagle's Nest," this ruined ancient city rests on a remote mountaintop.

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

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

Hidden just under the waters around this Turkish island are the ruins of a once great city.

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

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

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

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.

A marvel of Byzantine engineering under the streets of Istanbul.

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

Site of the 1889 murder-suicide of crown prince Rudolf and his lover Mary Vetsera.

An ornate private entrance to the Vienna subway built specifically for the emperor.

The topiary maze at the Habsburg hunting lodge.

The housing complex served as an anti-fascist fortress during the Austrian Civil War.

A neo-Gothic mansion now houses a wunderkammer of analog tech that hits on all the senses.

This former insane asylum now holds a pathological anatomy museum.

The former private quarters and office of Dr. Sigmund Freud now hosts a museum housing the works of the founding father of psychoanalysis.

Vienna's diversity-themed traffic lights were inspired by the Eurovision Song Contest.

Dine amidst exotic plants at this former royal greenhouse.

Museum devoted to the artificial language of Esperanto.