The world's largest wooden structure.

Spain's stunning solar energy plant.

The Roman city was the birthplace of various emperors and is home to one of the empire's most impressive architectural feats.

The ruins of an ancient stadium that hosted gripping chariot and horse races.

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

These "mermaids" that surround a plaza in Segovia are rather sphinx-like.

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

The remains of the second-oldest zoo in Europe can be seen within these library gardens.

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 lush indoor jungle fills this bustling Madrid transportation hub.

The 2,000-year-old Roman columns are hidden within Barcelona's Gothic Quarter.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

A beautiful but toxic fountain of mercury.

Barcelona's historic 19th-century sewers, whose foundations were laid in medieval times, are open to the public for exploring.

This former Baroque palace on the historic Calle Montcada is a rare architectural gem and was once the meeting place of an aristocratic scholarly society.

A cemetery in Barcelona's Poblenou district is home to this touching funerary statue, which depicts death in the form of a winged skeleton.

Barça football fans might see the insignia hidden in a church window as a divine sign.

A little slice of Japan and its aesthetics in London's Holland Park.

You'd never know the houses at 23-24 Leinster Gardens were fakes—until you see the train tracks on the other side.

An island on the Venetian Lagoon hosts this stone chair that has nothing to do with the King of the Huns.

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

A miniature village mimics the surrounding buildings so well it includes itself.

England's foremost purveyor of funeral furniture hasn't changed a bit since the 1960s.