Canyon walls shrouded in ferns.

The ruins of an ancient temple to the Aztec wind god discovered in the middle of a metro station.

Where layer cakes tower above one’s head and there is never a shortage of icing.

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

Part bookstore, part café, and part forest.

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

This 14th century castle withstood years of battle but is now sliding off the hills into the Danube.

Eccentric sculpture garden brings Basque mythology to life.

An abandoned nightclub has become a vibrant work of art.

There is a strange little carving of a person seemingly crushed by a pillar behind the remains of St. Thomas Aquinas.

This French castle is said to have once held the Holy Grail but is now a gorgeous mountaintop ruin.

This futuristic observatory at the top of the Pyrénées offers unrivaled views.

15,000 year old bison sculptures.

Abandoned blockhouses from Nazi Germany's Atlantic Wall erode into the sea on a French beach.

This religious complex carved into a cliff is steeped in legends of miraculous stags and the Holy Grail.

A Franco-era dam flooded (almost) everyone out of this centuries-old Aragonese town.

This huge abandoned fortress hidden inside a mountain holds a world of subterranean secrets.

The 43-mile route crosses through six islands with gorgeous views of the Seto Inland Sea.

An eerie collection of the surviving structures from a past celebration of the future.

A 16th-century Andalusian palace.

This former charity hospital for elderly clergy houses some of Seville’s most treasured paintings.

East London art gallery showcasing contemporary art from Europe's Eastern Bloc.

A sculpture outside London's oldest cathedral honors the Mohegan chief who died while petitioning the king.

The John Snow Memorial marks the epicenter of London's 1854 cholera epidemic.