This vast masterpiece of Moroccan architecture spreads across 20 acres.

Climb a steep hill in 90 seconds on the second-oldest urban subway in the world.

Legend says if you stick your thumb in the hole and it gets wet your wish will be granted.

A marvel of Byzantine engineering under the streets of Istanbul.

This small, ancient Roman temple was once a church dedicated to the patron saint of penitents.

This curious, round temple is the oldest still-standing marble building in Rome.

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

An ancient Roman temple first dedicated to an emperor's wife is now a church.

The remains of this 2nd-century Roman temple are incorporated into a modern building.

A detailed pachyderm supports Rome's smallest Egyptian obelisk.

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.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

Five candy-colored villages on the Italian Riviera.

A lover's walk between hilltop towns, decorated with graffiti love notes.

Some 80,000 Delft Blue tiles line the inside of this Amsterdam walkway.

This 22-floor tower's Skydeck offers panoramic views of Amsterdam.

An impressive armored bronze effigy marks the tomb of one of the medieval era's greatest warriors.

One of England's most famous churches hides a pair of little known architectural treasures.

Artists and musicians now rule over this former rail station.

The fierce beast perches atop a pedestal marking where the historic City of London gates once stood.

Hear the quietest sound from across the dome.

The ruins of a church destroyed by both the Great Fire of London and the Blitz, now turned into a peaceful garden.

This churchyard arbor is surrounded by hundreds of gravestones placed there by author Thomas Hardy.