Northern Ireland's Brobdingnagian stepping stones.

The atmospheric road was never meant to be so creepy.

This demon atop the Notre-Dame de Paris looks utterly bored.

The celebrated eyesore created by starry-eyed sweethearts.

The tradition of open-air secondhand and antiquarian bookselling in Paris dates back to the Renaissance.

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

This bridge was constructed from the rubble of the infamous Bastille.

The world's tallest bridge is also possibly the most elegant.

A natural arch carved by a river gave its name to the so-called "Cave of Forgotten Dreams."

Historic medieval fortified city in southwest France.

This salt marsh in Southern France is as pink as the flamingos that inhabit it.

The first green space constructed on an elevated viaduct.

19th century pendulum and a clock restored by a rogue group of guerilla artists.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

High atop the Eiffel Tower is a small apartment built exclusively to entertain the science elite and make the rest of Paris jealous.

This Roman arena once played host to bloody gladiatorial battles.

A New York–based physician returned home to Spain to build his own elaborate monument to Christopher Columbus.

This multi-level, aqueduct-footbridge hybrid is one of the greatest works of the Spanish Renaissance.

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

A magnificent, long-abandoned castle built in the wake of the reconquest of Spain.

This 47-story "M" needed 20 years to be completed

The Gaudí-inspired building that was the start of Terrassenc modernism.

This line of 12 tower mills described in the story of Don Quixote is among the most iconic landscapes in Spain.

An ancient Roman theatre restored to its former glory in the Spanish city of Cartegena.