Carved by a waterfall in a hard-to-reach rock formation, this heart-shaped rock has inspired romantics for decades.

This geothermal hot spring hides beneath a slowly growing mineral dome.

Quite simply the largest tree in the world (by volume).

Seattle's own bad art museum located inside Cafe Racer.

A sacred site for Native Americans surveyed by George Washington and owned by both King George III and Thomas Jefferson.

This naturally-sourced hot spring is now home to a clothing-optional resort.

The magic's in the hole!

The largest self-built castle in the U.S., six decades in the making.

The name of this famed hospital was once a byword for the horrors of medical and psychiatric care.

A tunnel once abandoned now thrives with graffiti art as an off-limits makeshift gallery.

Frank Lloyd Wright's most iconic home dangles over a Pennsylvania waterfall.

One of the dwarven trees dates back to 1625 and survived the Hiroshima bombing.

The world's longest known cave system.

A modernist landscape of water and sci-fi concrete.

These delicate buggers are some of the rarest fossils that have bubbled up from the Tar Pits.

A museum dedicated to the alleged Roswell Incident.

Collapsing castle on the Hudson river was once the storage site of military surplus business.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

A look into the Church of Scientology's deeply unfavorable view of psychiatry.

Where manatees are the snowbird vacationers in these balmy Florida springs.

Panorama exhibition hall in old silent theater with a beautiful backyard garden.

The longest continuous lava tube in the continental U.S. offers 2.5 miles of dark explorations for the adventurous.

This 4,000-foot-diameter hole is touted as "the most well known, best preserved meteorite crater on Earth."

This knobby, drooping New Orleans oak is a favorite place both for climbing and for meeting giraffes.