A historic trade hub teeming with gorgeous architecture, colorful goods, and vibrant designs.

The ancient necropolis houses the immense rock-cut tombs of four Persian kings.

A sinister pyramid in the Frari contains the heart of the famous neoclassical sculptor.

A copy of the famous statue can be found in this Florence piazza, along with one of the most breathtaking views of the city below.

These colorful French islands spent a stint bootlegging booze during American Prohibition.

This palatial spiral staircase was so unusual the name "snail" was given to the noble family who built it.

The palace window through which Protestant nobles flung two Catholic regents, thus sparking the Thirty Years' War.

Italy's third-largest Roman arena gives a peek into the underground operations beneath the ancient spectacles.

This picturesque horseshoe weir was first built in the 1600s to prevent flooding in the town of Bath.

A rare wooden coffin set vertically into the Gothic arch of an ruined church.

The gorgeous entrances into the city's underbelly look more like grand halls than subway stops.

Now harmless, this looming post struck fear into the heart of medieval troublemakers.

A rare example of an octagonal Catholic church.

This charming cobbled backstreet is the most Instagramable street in Paris, much to the residents' annoyance.

Overlooked by many, the two famous Scottish warriors guard the main gate of Edinburgh Castle.

A 16th-century fountain marks the site of a lost medieval cemetery once filled with mass graves.

The avant-garde design was able to bypass strict Soviet regulations on architecture.

Filled with goldfish swimming in a shallow pool of sea water, this ancient crypt is more wishing well than burial site.

These medieval skyscrapers dominate the skyline of this small Tuscan town.

A dismembered holy head stares out from her beautiful reliquary at the St. Dominic Basilica.

Hidden beneath the famous St. Peter's Basilica is a veritable city of the dead that may hold the remains of St. Peter himself.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

This Roman arch marks the location of an ancient gate at one of the Seven Hills of Rome.

An Italian crevasse filled with abandoned buildings gives visitors a look at the world without humans.