A labyrinth of ancient tunnels hidden below the city holds the ruins of 2,500 years of history.

This shining multicolored metro station deep under Naples is said to be the most beautiful in Europe.

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

Medieval torture techniques with a modern conscience.

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

The verdant mossy ruins of a Franciscan monastery lie in the remote Sintra hills awaiting exploration.

This unreal Portuguese palace looks as though it's made from a pile of different castles.

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

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

A curious carving hides on a marble column in the Mosque-Cathedral of Córdoba.

This amazing example of Valencian Art Nouveau looks more like a cathedral than a public market.

These magnificent city walls rise from the barren sun-baked Spanish plains like something straight out of a fairytale.

Hundreds of stone stairs and a winding medieval bridge connect this haunting Spanish island to the mainland.

The celebrated eyesore created by starry-eyed sweethearts.

One of Jeff Koons’s largest sculptures and his first commemorative work.

A fortified palace in the shape of a ship on the Thiou river.

If you look closely at the oldest bridge in Paris, you might notice hundreds of ugly faces leering from its sides.

The opulent home that inspired Tintin's Marlinspike Hall and the adventures within.

A well-preserved medieval village nested on a rocky outcrop and surrounded by a network of cliffs, natural bridges and canyons.

The mental institution where Van Gogh created some of his most famous work now allows guests to walk in the artist's footsteps.

A 14th century bridge built as a fortress, where the devil lurks on one of its towers.

This French ghost town from World War II has been left as a memorial to German atrocities during World War II.

Bordered by forest on three sides and the ocean on the other, the Great Dune of Pilat is the highest sand dune in Europe.

Abandoned blockhouses from Nazi Germany's Atlantic Wall erode into the sea on a French beach.