Once the tallest building in the world, this abandoned church is now a monument to the destruction of WWII.

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

This half-forgotten fortress was constructed by the Ottoman conqueror of Constantinople.

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

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

It's believed that this small church was connected to the Hagia Sophia via a secret tunnel.

The most metal church of all time was built in record time because of an international, pious pissing contest.

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

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

This crumbling medieval basilica once attracted pilgrims by the thousands to collect a miraculous dust that formed above the saint's tomb.

The alleged house of the Virgin Mary is tucked away in a park and nature preserve on Mt. Koressos in Turkey and is holy to both Catholics and Muslims alike.

Seven early Christians were sealed into a cave where legend has it they slept unharmed for centuries.

The ancient latrines of the Greeks, in all their public glory.

An underground network of massive stone arches and their skylit vaults support ruins of portico structures above.

This elevator was built in 1907 to connect two neighborhoods separated by a steep, rocky cliff.

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