A beautiful but toxic fountain of mercury.

Three bridges and one giant canyon make up this fantastic Spanish settlement.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

This semi-secret storybook hedge maze is also the oldest garden in the city.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

The mysterious remains of a martyred teenage saint are venerated inside a small country chapel.

Seaside ruins of a settlement that date back to the first century B.C.

The oldest Roman lighthouse still in use.

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

This cafe offers a curated collection of treats and tipples made by monks and nuns.

This coffee shop lies hidden beneath a historic church.

This 19th-century fountain's namesake animal isn't what you think it is.

A museum dedicated to the Spanish occult in a town that was terrorized by the Inquisition.

This Navarrese cave's history of witchcraft and pagan ritual is not just embraced, but recreated each year.

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

A landscape decorated with enormous skull sculptures.

A plaque marks the house in Stockholm where the French philosopher René Descartes lived up until his death.

A man has revenged his true love's betrayal through tears and stone genitalia.

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

There's an exclusive Beefeaters pub hidden in the Tower of London.

A spectacular hidden beach in Ireland has the dark, disturbing nickname of "Murder Hole Beach."

The severed head of a 17th-century Irish martyr lies within an intricate golden shrine.

A museum that cashes in on its infamous little people while teaching you a thing or two about the Irish fey.