Quite simply the largest tree in the world (by volume).

The second-largest giant sequoia in the world.

The world's largest wooden structure.

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

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

Single runway interrupted by a busy road that cuts across its middle.

This massive fiberglass Gulliver turns every visitor into a Lilliputian.

This house's itty bitty size means no humans allowed.

Of the many chalices in the running for the Holy Grail, this one in Valencia Cathedral sure looks the part.

This amazing example of Valencian Art Nouveau looks more like a cathedral than a public market.

A New York–based physician returned home to Spain to build his own elaborate monument to Christopher Columbus.

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

A lush indoor jungle fills this bustling Madrid transportation hub.

An ancient Egyptian temple in the middle of Madrid, Spain.

The oldest restaurant in the world is this old-world Spanish eatery, still known for its suckling pig.

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

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

A small window on Via Piella offers a lovely and rare peek at Bologna's lost canals.

Over 100 towers were built in Bologna during the Middle Ages, but only 22 survive.

In the world's oldest university is a stunning 17th century anatomical theater carved from spruce.

Legend has it this fountain built to symbolize the Pope’s power hides a strange secret concerning Neptune's manliness.

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

An underground city of salt.

This Polish cave has housed a dragon, a brothel, and an enduring legend.