A castle that was built stone by stone by an eccentric journalist.

Hundreds of glow-in-the-dark objects light up a museum in a historic zinc mine.

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

Odd outsider art installations surround a Gold Rush-era ghost town.

A historic neighborhood church is reborn as a psychedelic arts collective.

No one knows how this Pacific Northwest spruce tree came to have so many trunks.

Wild lights and sound effects turn a walk through some caves into an eye-popping 1960s tourist attraction.

These eerie outliers of the lightning bug family glow a mysterious blue color.

In a 345-million-year-old cave that's 200 feet underground, dinner awaits.

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

Towering basalt columns, a creation of fire and ice.

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

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

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

This frequently-photographed waterfall takes only a short hike to visit.

This incredible collection of vintage pinball machines can be played at 25 cents a pop.

Sniff the Titan Arum's rotting flesh.

A beautiful geyser under environmental threat.

Crypt mausoleum in cathedral's basement contains relics of third century Roman martyr, Saint Vibiana.

This unique structure in suburban Austin is made up entirely of other people's castaways, and constantly changing.

Seemingly grown on some other world, these New Mexico rock formations look like a disused science fiction set.

The first declared National Monument in the United States.

Its buzzing collection honors vibrator history.

Stepping away from the glitz of mobsters and casinos to learn about the other history of Vegas.