This Arizona observatory is famous for investigations into Martian life, and as the place humans first spotted Pluto.

The largest natural travertine bridge in the world is nestled in a small canyon in central Arizona.

The world's largest military aircraft cemetery.

Curious cave that stays a cool 56 degrees all year long.

At the tallest peak in Colorado, an electrifying mix of thin air, lightning, and rivalry.

A regular looking rock with an unbelievable history.

Deep scars on the earth left by the Ice Age.

The highest point in Washington state is a volcano covered in glaciers.

Once strictly off-limits, this lower level housing curious and priceless vehicles of the Petersen Automotive Museum is now open to the public.

Turnip-shaped island just off the Michigan shore in Lake Huron.

The quiet canyon has a tumultuous history involving a doomsday cult.

Named after a bandit and the star of several Hollywood prehistoric landscapes, these sandstone formations are a historical part of the Los Angeles natural landscape.

One of the most unusual geological features, recognizable from a dozen hit movies.

This funicular railway rumbles along for a mile up the nearly vertical face of Chattanooga’s Lookout Mountain.

The highest dunes in California are the most likely place in the area to hear the Singing Sands.

This freshwater spring fills with 10,000 gallons of water per minute.

A cave's rare beauty held a cavernous secret hidden underground.

These curious caverns have been home to mushrooms, gangsters, and disco.

Despite time, colonization, and the brutal New Mexican heat, these Pueblo ruins still stand.

Once a menacing challenge for trailblazers, this trail is now the most scenic drive in Utah.

The illuminated falls are a gem in North Cascades National Park.

Witnessing the might of this dessert-colored desert waterfall is a rare, powerful treat.

Come for the speed, leave in love with the desert.

A volcanic tunnel illuminated by natural skylights offers a shaded respite from the desert sun.