Tubing through a cave lit with glowworms is a magical underground experience.

The oldest Roman lighthouse still in use.

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

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

This makeshift concrete bunker is an unusual reminder of the Cold War.

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

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

A magical sinkhole on the Yucatán Peninsula is adorned with mini waterfalls and hanging vines.

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

These Egyptian statues have survived for 3,400 years and were an acoustic wonder of the ancient world.

These mountain hot springs have seen power struggles, doomed romances, and a generalissimo's attempted escape from mutiny.

An ancient fortification lives on in this Chinese city.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."