This ancient Roman prison is decorated with an upside-down cross not as blasphemy but as saintly tribute.

Jesus' footprints and the first catacombs in the world.

2300-year-old Roman road connecting the empire.

The underground sanctuary of a mysterious ancient cult.

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

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

Rome’s legendary peephole vista is also a former Crusader stronghold.

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

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

The birthplace of Karl Marx is now a museum dedicated to the communist revolutionary's life and work.

The last bastion of Roman presence north of the Alps looms over a German town.

Along the banks of the River Rhine lies a park that seems unassuming, but beneath the surface lies a long and fascinating history.

While you wait to cross the street at a traffic light in Mainz, you might notice that the light is staring back at you.

A historic casino where Dostoyevsky is said to have lost it all on a single spin of the roulette wheel.

This tremendous timepiece was once the largest cuckoo clock in the world.

The final resting place of the famed German pilot, the "Red Baron."

A rare water-powered funicular, it uses a huge tank of water and gravity to do its work.

Fantastic views and thousands of love locks.

The entrance to this Frankfurt subway station looks like an old tram car crashed into the concrete sidewalk.

An accidental trick of light casts the perfect shadow of a pilgrim of the Camino de Santiago against the cathedral wall.

This enormous censer uses a pulley system installed over 400 years ago.

Eat the ultimate iteration of Portugal's most beloved pastry.

Sip cherry liqueur at a bar dating back to 1840.

Portugal's National Pantheon has a history of curses, collapses and financial problems.