An abandoned theme park with a strange and tumultuous past.

One of Frank Lloyd Wright's greatest—and favorite—architectural masterpieces was almost lost.

This sprawling collection of saintly relics includes such fascinations as wood from the Cross of Jesus and threads from Mary's veil.

A forsaken wonder in the middle of the East Side neighborhood.

The world's longest known cave system.

A natural gas leak provides a flickering flame beneath a waterfall.

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

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.

The ruins of a town wiped out by the second-largest earthquake in recorded history.

This small city where almost everyone lives in the same building can only be reached via North America's longest tunnel.

Ruins of a once-prized railroad station in New York.

A walk-in working camera obscura produces 360-degree live images of the San Francisco coast.

The seawater playground of gilded-era San Francisco burned to the ground in 1966.

Upside-down trees serve as natural flower pots in this hanging garden of Alaska.

A rare chance to get up close and personal with a 13-mile ribbon of ice near downtown Juneau.