One of the few remaining ancient aqueducts described by Frontinus as 'the most solemn testimony of the Empire.'

A haven for book enthusiasts across the street from Retiro Park.

Commonly acknowledged as the only public monument to the Devil himself.

Madrid's romantically ornate crystal palace has been offering shelter to plants and art for over a century.

An iconic and controversial ancient Iberian funerary urn with a hauntingly penetrating gaze.

These ancient artifacts are a testament to the enduring significance of the bull in Spanish culture.

This enigmatic artifact is a rare depiction of an ancient Iberian noblewoman.

This enigmatic Iberian sculpture of uncertain origin may have once guarded a burial site.

This embalmed man is one of the best preserved mummies from the Canary Islands.

This generously endowed statue once stood guard outside a Roman home.

A hidden workshop for creating and restoring Papal mosaic masterpieces.

The doodles of a genius line the walls of a secret room under the Medici Chapel, where they were hidden for nearly 500 years.

This Roman statue is missing a limb from when the Venetians stole it from Constantinople during the Crusades.

Go inside to really appreciate this 500-year-old technological masterpiece.

This concrete tangle of square pipes has stood as a proud thorn in the city's side since the '70s.

San Francisco's newly reopened hands-on science museum.

A man-made island in scenic San Francisco Bay.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

From the sky, a kaleidoscope of color brightens the grey landscape of the San Francisco Bay.

A small marionette collection located within the dark cellars of an 11th-century Austrian castle.

Epicurean and holy traditions converge in what may be the oldest restaurant in Europe.

These 12th-century catacombs carved into a mountainside were a place of mysticism and Christian hermitages.

Ugly 18th-century dwarf statues living in a perfectly landscaped Austrian garden.

King Ludwig I's collection of beautiful women.