A perfectly circular lake is formed by the crater of an ancient underwater volcano.

One of the best-preserved medieval streets in Europe.

This former Imperial summer home was the venue for a royal slap that once echoed 'round the world.

This crucial gathering spot along the "hippie trail" still displays old notes between traveling beatniks and backpackers.

A marvel of Byzantine engineering under the streets of Istanbul.

A fountain standing as a testament to a doomed alliance.

Turkish adventurer antiques in the heart of the Grand Bazaar.

A meow-velous tribute to a beloved street cat, made famous on the internet.

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

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

A giant replica of an Assyrian cuneiform tablet stands in the middle of a busy intersection near the city center of Kayseri.

This arch granting triumphal entrance into Antalya was designed to honor the emperor's visit.

A gorgeous, Gaudí-esque stairway constructed in the city of Istanbul by a prominent Jewish family.

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

A surprising and unconventional mosque hidden in the subsoil of Istanbul.

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

An abandoned Byzantine fortress and notorious prison.

One of the most photographed locations in the entire city.

The oldest olive tree in Greece has been bearing fruit for at least 2,000 years.

A small island with shimmering pink sands, home to loggerhead turtles and rare plants.

This stone tower was built to protect Crete from incoming pirates.

Whitewashed mosque contains the world's largest carpet.

This replica of the Greek structure is in the heart of Nashville.

The inventor of a number of hybrid corn species is immortalized with a field of giant corn.