One of the most colorful free outdoor attractions in San Diego, this park is filled with murals and ties to history.

An inconspicuous footbridge beloved by San Diego locals.

Tijuana's legendary jai alai or "basque ball" palace is now a massive music venue.

The original home of the Caesar Salad.

Giant nude woman of Tijuana is also the artist's home.

Macabre astrological automaton clock dating to the late 1400s.

Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.

A series of playful yellow penguins share a serious message about the environment.

A plaque marks the spot where the saint was shoved off the Charles Bridge and into the river.

A half-buried vehicle in Prague's is the latest iteration in a long-running piece by Czech artist David Černý.

This London pub hides a peculiar secret: a recreation of the rooms shared at 221b Baker Street by Sherlock Holmes and Dr. Watson.

The John Snow Memorial marks the epicenter of London's 1854 cholera epidemic.

The Great Fire of London and the regulation of one-way streets both started in this alley.

The commemorative stone column conceals a secret laboratory.

This statue of one of the engineers who created the London Underground hides a ventilation shaft for the tube lines that run under the street.

Catacombs turned marketplace.

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

A hidden treasure in London with a rich medieval history, and the resting place of many luminaries.

This beautiful 19th-century temple stands atop the ruins of its predecessor.

A 50-foot tile mural mosaic for the 100-year anniversary of the Statue of Liberty.