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

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

Six ravens are kept captive (but well-fed) at the Tower of London to prevent the fall of the Crown.

Scattered throughout London are ancient remnants of the city's former bounding wall.

Eighty million natural history specimens call this gargantuan museum home.

Kings Cross Station pays tribute to its role in Britain's best-selling book series.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

This outdoor library provides around-the-clock access to around 7,000 books.

The monumental home of Prussia’s eccentric "Cannon King."

Remnants of a cone-shaped Nazi bomb shelter.

A Black Forest cuckoo clock theme park features one timepiece big enough to walk inside.

This small church was constructed over the ruins of three temples dating to the Roman Republic.

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

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

A monumental fountain in Rome features a large statue of Moses that has been criticized for centuries.

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

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

One of Catholicism's four major basilicas has a series of papal portraits that are said to predict the end of the world.

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

Stone memorial that's said to predict the death of the pope and the site of the Cadaver Synod.

In the early Roman Empire, people deemed traitors and criminals were tossed to their deaths from this rock.

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

A detailed pachyderm supports Rome's smallest Egyptian obelisk.

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