Huge concrete structures designed as an early warning system for Britain to detect enemy aircraft.

A house of bones — but nobody is quite sure to whom they belong.

Madrid's romantically ornate crystal palace has been offering shelter to plants and art for over a century.

One of the few remaining ancient aqueducts described by Frontinus as 'the most solemn testimony of the Empire.'

Commonly acknowledged as the only public monument to the Devil himself.

An ancient Egyptian temple in the middle of Madrid, Spain.

Over two centuries old and counting, Madrid's massive botanical garden contains one of Europe's only desert environments.

This "City of Books" holds a museum, library, and the complete personal book collections of five of Mexico's greatest thinkers.

Superstitious? Discover the witchy side of Mexico through its largest esoteric market.

An airy Art Deco space devoted to the weird and wonderful folk art traditions of Mexico.

CDMX's home for the world's culinary delights.

An Aztec temple, the largest man-made pyramid in the world, sits buried in earth with a Spanish church set on top.

An indigenous take on European design creates a stunning visual overload.

The ruins of an ancient city built by Mayan traders is centered around a temple of a sacred feathered serpent deity.

High atop a Mexican rainforest mountain, this ancient pyramid once drew pilgrims countries away.

An island filled with hundreds of hanging, decomposing, decapitated dolls.

Frida Kahlo's childhood home, now a museum of her life and works.

This giant expressionist head crowns a museum devoted to a beloved Mexican leader.

This incredible college library is a visual masterpiece of mosaic art. It also looks kind of like a giant boombox.

Twelve natural mummies are displayed in the crypt of this former monastery school.

The famous artist couple lived and worked here, in two different houses separated by a bridge.

A museum in the former home of Marxist revolutionary Leon Trotsky.

Diego Rivera's massive tiled fountain and failed infrastructure project.

Part bookstore, part café, and part forest.