These ornate arches show how the course of the River Thames has changed.

London's smallest police station is barely the size of a phone booth.

This ordinary street was made infamous by a legendary visit from the devil.

Rebuilt remains of a temple to Roman god Mithras.

The pretty iron lamp is a reminder of the architecture underneath London's streets.

Classic game cookery takes center stage at what's widely considered London's oldest restaurant.

The bronze uniforms commemorate the vital role of women during World War II.

A statue of the legendary Celtic warrior queen who fought the Roman invaders stands in one of the cities she once destroyed.

One part local history, 99 parts gruesome haunted house.

These official units of measurement—including chains and perches—lie hidden beneath tourists' feet in a popular London hub.

These hut foundations are believed to be the residence of Romulus, founder of Rome.

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

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.

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

These wire animal sculptures commemorate the exotic inhabitants that once called the Tower of London home.

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

An 18th century fountain and two columns are all that remains of Rome's forgotten river harbor.

Rome's first modern graffito is all that is left of a peaceful protest from the 1970s.

A massive marble foot is tucked away in a small alley near the Pantheon.

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

Tucked away in the Tower of London is the weapon once used to execute high-profile prisoners.

Richard III supposedly disposed of his nephews' bodies here in an effort to seal his claim to the throne.

Graffiti from the 16th and 17th centuries cover the walls of this part of the Tower of London.