The once forbidden "secret cabinet" of erotic art from excavations of Pompeii and Herculaneum.

Iconic red and white plaques show the creative names invented to navigate the city streets.

A flooded Mexican cave that hides a river beneath the water.

Clap your hands at the base of the pyramid, and the song of a sacred Mayan bird will echo through the air.

An elaborate Mayan city shrouded in alien conspiracy revealed the tomb of Pacal the Great.

No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

Every equinox this Maya pyramid puts on a spooky ancient light show.

The alleged house of the Virgin Mary is tucked away in a park and nature preserve on Mt. Koressos in Turkey and is holy to both Catholics and Muslims alike.

A charming beach town in Turkey captures all the colors of the rainbow.

Carvings in Turkey's Marble Road may have directed ancient Romans to a hidden brothel.

Museum celebrating the ocean, with the largest wunderkammer dedicated to sea exploration.

Look closely and you’ll notice that the color changes a third of the way up the tower.

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

The unique traffic pattern named for an influential urban planner is also known as the Pedestrian Scramble.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

Rome's semi-secret peephole vista is also a former Crusader stronghold.

To find the "unicorns of the deep" you've got to go downstairs.

Years of archaeology, just chillin' by the water cooler.

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

One of the largest underground systems runs under Canada's largest urban center.

One of the Seven Wonders of the Modern World holds the world's tallest metal staircase.

Replicas of Apollo's leonine stone guard cats still line a sacred row in Greece.

A Bronze age settlement on the Greek island of Santorini might have been the inspiration for Plato's Atlantis.