One of the largest-ever mental hospitals now sits abandoned, surrounded by 25,000 unmarked graves.

Clap your hands at the base of the pyramid, and the song of a sacred Mayan bird will echo through the air.

No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

Every equinox this Maya pyramid puts on a spooky ancient light show.

A lush indoor jungle fills this bustling Madrid transportation hub.

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

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.

An oasis of calm amid the chaos of the boardwalk, the museum traces the heritage of this beloved beachside amusement park.

This outdoor gallery of graffiti-covered walls pays homage to the past, present, and possible future of street art.

One of the most enjoyable bits of history at Coney Island and “the most romantic ride in the world.”

You can still ride this 100-year-old work of art in Brooklyn's largest public park.

A formerly glacier-tipped volcano that inspired none other than Jules Verne.

Walk in the footsteps of the gods and straddle two tectonic plates.

Medicinal spa created with the discharge from a geothermal energy plant.

This scenic Icelandic lava flow is named for a pair of Berserkers who were murdered, according to a famous Saga.

The largest whale museum in Europe allows visitors to walk among life-size giants.

One of the tallest buildings in Iceland, and perhaps, the most visually impressive.

This stunning concert hall has become a symbol of Iceland's national recovery.

An encyclopedic collection of mammal penises.

The picturesque birthplace of Icelandic democracy is drenched in the blood of its brutal past.

This beautiful, historic church looks like something out of a simpler past.

These ominous lava formations were said to be an entrance to the netherworld so of course they inspired a famous metal band.

If a glacial river suddenly diving into a sheer chasm via a dramatic, multi-stage waterfall isn't peak Iceland, it's certainly close.