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

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

The remains of this misplaced church were moved here stone by stone.

Once a resting spot for King Fernando VII.

This small museum tucked within a subway station holds pieces from Madrid's past.

Among the oldest structures in Madrid, these Moorish walls once guarded the medieval city of Mayrit.

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

Two stone columns flank the grand Venice square, but there were supposed to be three.

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

It took more than 300 years to build this church, which is home to two sacred vessels believed to hold the blood of Christ.

Pilgrimage site for star-crossed lovers.

A cone-shaped top and cylindrical body set this 900-year-old structure apart from other Italian bell towers.

The world's most active stratovolcano is almost always erupting.

A mysterious ancient elephant said to possess magic powers is now the symbol of a Sicilian city.

Replicas of fossils unearthed during renovation work reveal how this area would have looked millions of years ago.

One of the oldest and most significant collections of Ancient Egyptian archeology outside of Egypt.

A fake medieval village in the middle of Turin.

An expansive collection of vehicles and other paraphernalia marking the history of firefighting.

The oldest church in Mantua was buried for centuries under the facades of other structures.

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

This awkward aquarium sculpture is one of the strangest statues in Chicago.

This small, ancient Roman temple was once a church dedicated to the patron saint of penitents.

This curious, round temple is the oldest still-standing marble building in Rome.

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