Remarkably intact Roman stone fortifications have encircled this Spanish city for centuries.

"Satisfying" is a good way to describe these beautifully aligned rows of Spanish mills.

Open air sculptures by an eccentric and loin-clothed hermit.

This panoramic lift provides a futuristic ride up San Pedro Mountain.

The remains of an encyclopedic sculpture garden later used as an internment camp.

Natural stone arches form a walkable "cathedral" at low tide, then disappear entirely when the water returns.

The celebrated eyesore created by starry-eyed sweethearts.

A mechanized clock where a man fights off a dragon, crab, and rooster.

During the summer months, giant teddy bears take over Paris near Les Gobelins metro station.

The industrial architecture honors the laborers who brought the Exposition Universelle of 1900 to life.

Remains of Roman amphitheater hidden in a sleepy quarter of Paris.

Once a 19th-century brasserie, this McDonald's exterior celebrates Alsatian design and the "King of Beer."

A lone cannonball remains lodged in the walls of the Hotel de Sens as a sober reminder of a revolution.

Natural history museum celebrating biodiversity with a parade of taxidermy animals.

The curious underground history of keeping Paris clean.

Egyptian Revival movie palace abandoned for decades and restored in 2013.

This statue was given to France by the United States to commemorate the centennial of the French Revolution.

This charming cobbled backstreet is the most Instagramable street in Paris, much to the residents' annoyance.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

The oldest stone house in Paris was built by its most famous alchemist.

Notorious artist squat renovated into legal studios.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

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

Designed to resemble foreign architecture, this mosque-looking structure was used to pump water to a royal fountain.