A mountain cave is the site of archaeological findings and Paleolithic rock art.

San Gennaro, the patron saint of Naples, greets pedestrians between these narrow city streets.

Come face to face with the ferocious visage of the serpent-headed mother goddess of the Aztecs.

This colossal ancient jaguar sculpture was used as a vessel for the hearts torn from sacrificial victims.

This ancient structure was built by a mysterious civilization that was largely destroyed by a volcanic eruption.

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

St. Mary's features one of the most spectacularly decorated cathedral interiors in all of Europe.

The former Nazi Germany concentration camp stands as a museum to remember this dark chapter in European history.

An underground city of salt.

The chaotic studio of one of the 20th century's most important artists has been preserved down to the dust.

The house where the writer spent his formative years.

For decades, Puerta del Sol has been illuminated by a giant, guitar-wielding bottle of sherry.

This sweet-toothed bear searching for snacks has been a symbol of Madrid for decades.

A stone slab in Madrid marks the point from which the distances of Spain's national roads are measured.

The design of this beautifully crafted building was inspired by Norwegian glaciers.

One man's exploration of the human form, including the bizarre and delightful "Man Attacked by Babies."

The original toys that inspired the beloved children's stories are on display at the New York Public Library.

The only castle in North America to ever house European sovereigns.

The Tudor-style cottage in the middle of the square is not quite what it seems.

A lush indoor jungle fills this bustling Madrid transportation hub.

A Christian monastery stands on what was once a holy Incan temple.

An Inca spa, military outpost or maybe… both?

Built on the remains of one the Incas’ most important gathering spots, this square keeps the spirit of a fallen empire alive.

Situated on a sacred Inca site, this 16th-century cathedral took nearly 100 years to build.