According to legend, this cavern holds the passage that Persephone used to travel to and from the underworld.

Inside this art museum resides one of Glasgow's most famous musical instruments.

This hidden oasis features a stunning view of the Hudson River and the Palisades from a castle-like museum.

Quite possibly the oldest love poem known to humankind.

Try a classic Necco candy bar being resurrected in a small suburban shop.

A physical reminder of Earth's ancient past, this rock results from the photosynthetic processes of some of the oldest forms of life.

A small cell adjacent to this church was once the bedroom for a renowned saint.

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

The spot where the fascist dictator made some of his most famous speeches including declaring war on Britain and France.

More sculpture than building, this architecturally significant temple was built on the spot of Saint Peter's crucifixion.

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

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

A man's head is enshrined beneath a statue near the first building constructed for the modern Olympic Games.

The oldest standing Byzantine church in Athens is tucked within a monastery in the middle of an upscale shopping district.

A statue representing a lost Roman profession that was vandalized for centuries.

A deep mark on the remains of a Roman temple, believed to be left by a legendary warrior.

A Byzantine-era church hidden in a wooded area below the Acropolis.

Remnants of a 4th-century church with vivid medieval frescoes and ancient sarcophagi hide beneath this old basilica.

A fortified medieval basilica on the Caelian Hill preserves extraordinary frescoes and one of Rome's most beautiful hidden cloisters.

Legend says it was constructed with the destroyed pillar of an ancient Greek Temple.

Plaques on its facade commemorate the Tiber's most destructive deluges.

This Roman relic was discovered in Scotland by a mudlarking ferryman.

This historic structure has been used as a mosque, a barracks, a prison, a school, and a bakery.

Even for Egyptian royalty, the afterlife was bring-your-own-beef.