This historic Amsterdam bar used to accept sailor's monkeys as payment.

This city square is home to Amsterdam's oldest church and a statue honoring Dutch sex workers.

A Dutch passageway's artistic, aquatic-themed makeover pays tribute to the capital city's famed waterways.

Europe's official "zero-level," the equator of elevation.

Amsterdam's former hotspot for public executions and dissections.

The former headquarters of history's oldest megacorporation.

An ancient passage filled with stalls selling used books, once frequented by Vincent Van Gogh.

A unique work of automotive art calls this shopping center home.

For the holidays, the tallest broadcasting tower in the Netherlands turns into one of the world's tallest Christmas trees.

Thousands of tourists and residents in Cologne affix "love padlocks" on the Hohenzollernbrücke Bridge to symbolize their affections.

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.

This is the oldest Roman-made bridge in the city still existing in its original state.

The only remaining arch of the oldest stone bridge in Rome stands in the middle of the Tiber.

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

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

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

A rare example of a medieval house in Rome adorned with a melancholic inscription.

This ancient Roman arch misled treasure hunters for centuries.

This medieval church in Rome was almost destroyed following a terrorist attack in 1993.

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

A sculpture serving as an homage to Pope John Paul II.

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

This one-of-a-kind Roman arch is not actually dedicated to the god Janus.