Also known as the Square Colosseum, this building is a prime example of fascist-era rationalist architecture.

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

The engineering wonder and pleasure dome of a much-maligned emperor still holds undiscovered secrets.

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

The "dragon babies" of southeastern Europe.

When a supermarket opened up shop within a medieval building it became protected by UNESCO on a technicality.

Historic fortifications form the boundary of Vatican City, but it’s not entirely surrounded by walls.

Breathtaking and huge 430 year old maps of Italy.

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

This Niagara Falls tourist trap is a world bright with neon and curiosities that will inspire love, hate, or a mixture of both.

A floating cat sanctuary on an Amsterdam canal.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

Despite attempts by local police to discourage it, Beatles-inspired graffiti has been a means for artists to air grievances for decades.

Synagogue built from the stones of Solomon's temple contains the golem of Prague.

An eerie, existential museum dedicated to the author of "The Metamorphosis."

This tipsy office building in downtown Prague was originally called “Fred and Ginger.”

Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.

Macabre astrological automaton clock dating to the late 1400s.

The history of occult science is turned into a creepshow at this lurid Prague tourist attraction.

Gods clash with machines in a power plant regenerated as a museum.

This ancient market is often referred to as the oldest shopping mall in the world.

This subterranean shrine beneath a bike rental store celebrates the iconic Italian scooter.

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

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.