Home to what was once considered the largest gate in central Asia.

This "tower of death" has acted as an observatory, a religious hub, and an executioner's lair.

Light still pours into the ruins of this ancient Islamic observatory.

The Avenue of Mausolea is a series of grand palatial tombs.

This unreal Portuguese palace looks as though it's made from a pile of different castles.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

At this rare mosque in Tbilisi, Sunni and Shia Muslims pray side by side.

The last standing example of an ancient district's teatime tradition.

A cluster of historic bathhouses built on the famed hot springs that gave the Georgian capital its name.

You'll find just about anything in this funky Tbilisi flea market.

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

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

One of the most exquisite Lycian hilltop citadels in Turkey.

At this ancient settlement at the foot of Mount Babadağ, honeycomb tombs are carved into a round cliff.

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

This secret coastal village is studded with pastel-colored houses all piled on top of one another.

Swarms of dainty flying insects swarm into the Petaloudes Valley to get busy.

The final resting place of one of the brightest physicists of the 20th century.

The library's graceful rotunda is like a bibliophile's temple.

It houses the remains of a 17th-century version of the Titanic.

An illuminated manuscript comprising the life's work of a lone monk, inexplicably decorated with a portrait of Satan himself.

A striking symbol of the Bulgarian capital.

The colonial city's social history is reflected in its fanciful door knockers.

This elegant Colombian fortress was one of the torture headquarters for the Spanish Inquisition.