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

The yawning maw of this pagan visage is said to bite off the hands of liars.

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.

This hill made entirely of ancient Roman jars was simply a garbage dump to the people of the time.

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

The engineering wonder and pleasure dome of a much-maligned emperor still holds undiscovered secrets.

This ominous Albanian fortress houses tanks and downed planes as a reminder of their victories over Western imperialism.

A dead saint, a deadly poison, and a mysterious holy ooze.

An 18th century wonder of the world, lost in WWII, re-created at the Catherine Palace.

Walk along the medieval fortifications that have been protecting Tallinn since the 14th century.

A medieval setting reimagined into a unique art alley.

An empty relic of the Moscow Olympics crumbles away in Estonia's capital.

An ancient Viking runestone hidden in plain view in Stockholm's old town.

It houses the remains of a 17th-century version of the Titanic.

A whimsical bridge adorned with decorative dragons.

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

Once an opulent Art Nouveau hotspot, the Constanța Casino is one of Romania's most beautiful abandoned buildings.

This statue of the great Argentinian car driver is located near a famous curve of the Monaco Grand Prix.

Legacy of the earthquake that nearly wiped Lisbon off the face of the Earth.

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

Elaborately carved to showcase the glorious wealth that the age of exploration brought to the Portuguese empire.

Eat the ultimate iteration of Portugal's most beloved pastry.

Legend says this sacred tree was a gift from goddess Athena.

A marvel of Byzantine engineering under the streets of Istanbul.