Spanish architects used seized Muslim gravestones to rebuild parts of the fortress.

A curious carving hides on a marble column in the Mosque-Cathedral of Córdoba.

Spain's unique Mosque-Cathedral has been a place of worship for both Muslims and Christians throughout its history.

Spain's largest bullring offers a unique glimpse at architecture and history.

This restored Portuguese cafe may well be the most beautiful place in the world to grab a Big Mac.

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

Giant topiary dog once played a role in a terrorist bomb plot.

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

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.

The atmospheric road was never meant to be so creepy.

These barriers stand as stark reminders of Northern Ireland's troubled past.

This Victorian-era public house has set the standard for pub-style elegance for over a hundred years.

It was once nicknamed "the most bombed hotel in Europe."

Traveling this mountain pass reveals quaint stone buildings, stunning Irish scenery, and a bridge said to grant wishes.

This 30-foot pile of rocks may be the grave of a mythological Irish queen.

These murals stand as reminders to the troubled history of this Northern Ireland city.

A Mayan village preserved for centuries in volcanic ash.

Millions of glowing microscopic organisms light up the waters of this luminous lagoon.

Every fall this lake mysteriously drains, like a bathtub with the plug pulled out.

Ancient cliffs resembling a kilt on Scotland's second largest island emit an entrancing sound.

This Scottish museum is the only one in the world to focus not on one religion but all of them.

Displaced highlanders would take shelter from the wet Scottish climate under the large walled bridge at Glasgow Central Station.

An icon of the Battle of Britain is frozen in flight in a grand Victorian museum.