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

This ancient trail climbs the mountain where a Latin League cult worshipped Jupiter, its main deity.

A forgotten "city of water" underneath the famous Trevi district.

Inside this McDonald's you can dine on your Big Mac and fries next to a 2,500-year-old Roman wall.

The "Greatest Sewer" of ancient Rome is one of the oldest sewer systems in the world, and is still in use.

This hill made entirely of ancient Roman jars was simply a garbage dump to the people of the time.

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

Installed in an act of one-upsmanship, the annual sundial in this church is also a symbolic victory for the Gregorian calendar.

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

The martyr's wax-enhanced skeletal remains lie preserved in a glass case in the Santa Maria della Vittoria in Rome.

Architectural monsters are devouring this palace's every door and window.

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

At the crypt of St. Mary of Eulogies and the Dead you are left alone to ponder mortality among piles of skulls.

The underground sanctuary of a mysterious ancient cult.

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

2300-year-old Roman road connecting the empire.

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

This hidden Art Nouveau courtyard is an opulent feast for the eyes.

The famous artist couple lived and worked here, in two different houses separated by a bridge.

Thirteen sculptures in central Moscow graphically depicting vices of the modern world.

This building holds the embalmed remains of the leader of the Bolshevik Revolution.

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

Dr. Strangelove-esque tours reveal the inside a bunker once reserved for Stalin himself.

Moscow's other, lesser known kremlin is a fairytale-like cultural complex modeled after Old Russia.