This 18th-century pond is one of the main attractions in the Jardín del Príncipe in Aranjuez.

Abandoned Nazi train station turned underground astroparticle laboratory.

This arch granting triumphal entrance into Antalya was designed to honor the emperor's visit.

One of the best-preserved remains of "Tokyo's lost rivers."

A 12th-century castle featuring a sensory path where partially-sighted visitors can experience regional history through touch and sound.

The remains of the medieval wall that once surrounded Paris with ties to the construction of the Louvre.

Rare karst landscape eroded from a flat seabed.

Before it was buried by volcanic ash, this fast-food restaurant fed the hungry hordes of ancient Rome.

The tunnel's elegant proportions keep you snug with no claustrophobia freak-out.

This house covered in small stones was the work of one man over the course of nearly 30 years.

Some believe that the artist behind this whimsical statue inserted his own likeness as a way to discreetly flip the bird.

An air of mystery pervades this modern-day singing Stonehenge.

The remnants of the base where US Army troops learned how to fight in extreme conditions.

A museum of carnival attractions where you are invited to ride the rides.

At least according to the Guinness World Records.

Visit 17th-century ruins on a strikingly beautiful riverside walking trail.

The small Spanish town that played an important role in a human's first steps on the moon.

An outsider folly near Madrid.

The abandoned ruins of a beautiful medieval castle just outside Barcelona.

A once-secret library of Freemason history in Catalonia.

A once grand hotel now sits eerily abandoned in the Catalan countryside outside Barcelona.

Village situated on a narrow volcanic escarpment.

An enchanting monastery in the Spanish countryside appears lifted from a fantasy tale.

A series of recreated fortifications mark George Orwell's path through the Spanish Civil War.