Perhaps the most spectacular grotto along the Algarve coastline.

You can cross from one country to another in a single hop on this little bridge.

Some 4,000 individual tiles make up this striking blue billboard from the golden age of air travel.

Located in the thermoelectric factory that once powered the entire city, this Portuguese museum is shockingly fascinating.

This ancient altar emerges from the thick forests to reveal the mysteries of Etruscan sacrificial rituals.

A 16th-century horror show built in a lovely Italian garden.

This quaint Italian town keeps losing ground as the sides of its plateau slowly erode.

Nine caves filled with recently-discovered archaeological finds under the houses and the streets of the most ancient district of an old town.

This picturesque Umbrian city has a subterranean side that has long remained hidden.

A whimsical brother of the nearby Fallen Angel statue takes the falling part quite literally.

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

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

The walls and streets of the ancient city are peppered with penises.

Pompeii's less famous neighbor is still revealing her secrets.

It may take some time to locate, but it's sure to warm even a heart of stone.

Home to the largest urban bat colony in North America, estimated at 1.5 million bats.

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

A display of torture devices used in the Spanish Inquisition and other scourges of medieval Europe.

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

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

This magnificent castle grew from a small Moorish fortress, and reportedly inspired two iconic Disney castles.

The first mechanized factory in Spain is also one of the most significant mints in the history of money.

A curious memento mori hangs in the magnificent Cathedral of Segovia.

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