An alchemist's “magic door” stands in the middle of a Roman park.

This former Roman Catholic Church still contains the embalmed hearts and organs of 22 popes.

Breathtaking and huge 430 year old maps of Italy.

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

One of the most important yet well-hidden museums dedicated to the history of medicine.

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

This Italian stadium makes liberal use of fascist statuary to evoke classical sporting arenas.

Stone memorial that's said to predict the death of the pope and the site of the Cadaver Synod.

A mysterious chasm in the heart of the ancient Roman Forum, the Lacus Curtius was once believed to be a gateway to hell.

The yawning maw of this pagan visage is said to bite off the hands of liars.

One of seven Jewish catacombs in Rome and one of only two open to the public.

A museum cafe showcases Native American dishes and indigenous ingredients from across the Western Hemisphere.

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

The most accurate timepiece in the world.

The most decorated dog of World War I is preserved in the Smithsonian.

The winding route passes through an enclosed alleyway, two tunnels, and leads to the White House basement.

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

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

A 2,000-year-old computer demonstrates remarkable engineering and astronomical precision.

This mystical orb covered in strange symbols is thought to have been used in ancient Greek magical rituals.

The hallucinogenic center of the ancient world.

A cave network located at the southernmost tip of mainland Greece was once believed to be an entrance to Hades.

This legendary city has been a tourist attraction for centuries.

The final resting place of two (or three) presidents, one vampire, and 18,000 Confederate soldiers.