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

Spain's unique Mosque-Cathedral has been a place of worship for both Muslims and Christians throughout its history.

Holy Grotto of Montserrat Monastery holds one of Europe's mysterious black Madonnas.

Stunning Roman aqueduct used for 1900 years and still standing.

A former steam-powered mill from the 1800s is now an industrial park with a giant steel dragon slide.

Village situated on a narrow volcanic escarpment.

This whimsical winery by Antoni Gaudí looks ripped from the pages of a fairytale.

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

Next to the Leaning Tower of Pisa is a cemetery home to ancient sarcophagi and disturbing murals.

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

Geometry and mystery come together in an epic show of octagonal masonry.

This ancient trail climbs the mountain where a Latin League cult worshipped Jupiter, its main deity.

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

A detailed pachyderm supports Rome's smallest Egyptian obelisk.

Art and armour fill every inch of this rich kid's Italian villa.

These "anatomical machines" are only one of the many strange items in this Italian crypt.

The once forbidden "secret cabinet" of erotic art from excavations of Pompeii and Herculaneum.

A fire once nearly devoured this gorgeous 14th-century Gothic cathedral.

The European towns of Brașov and Râșnov each have proud signs reminiscent of the Hollywood sign.

This bone-filled cave got its name after they found 140 bear skeletons inside.

This communist behemoth is the heaviest building in the world and a legacy of a brutal regime.

Something's watching you.

This elaborately decorated, fairytale-like Romanian royal palace is one of the most striking castles in Europe.

The possible imprisonment of Vlad the Impaler here earned the medieval castle its nickname, "Dracula's Castle."