Long tunnels run under the ancient chariot racing circuit to the tower.

Stunning Roman aqueduct used for 1900 years and still standing.

The fragmented remains of a massive public bath connected to the city's water supply.

Once the grandest synagogue in medieval Spain, it now stands as a memorial of the 15th-century Jewish exile.

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

This macabre masterpiece of a mural is one of Francisco Goya's "Black Paintings."

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.

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

This 6th-century church has the largest and best-preserved collection of Byzantine mosaics outside Constantinople.

Ancient snack bar of the Roman Empire re-opened.

Water and windows define this defensive Italian well.

This strange bovine gargoyle is said to have been put in as a passive aggressive form of revenge.

Renaissance hospital featuring a rotating door into which unwanted babies were dropped.

The graveyard is filled with beautiful funerary art and boasts breathtaking views of Florence.

This 1st-century CE Roman bath sits under a carpark.

The Emperor Tiberius' palace of debauchery.

This clifftop arch is a natural stunner.

Was this cave created by Hercules's wrath, the devil, or volcanic activity?

A lavish 16th-century mansion filled with spectacular staircases, fantastic frescoes, and gorgeous gardens.

This tile-work piece featuring a chicken riding in carriage is both a remarkable artistic creation and a social commentary of politics and culture in 17th-century Portugal.

"Portugal's Stonehenge" is made up of nut-like stones aligned with the heavens.

A hidden three-foot-wide house separates these two regal churches.

A stunning 18th-century site where pilgrims ascend by a series of punishing stairs only to return via funicular.