The world's largest mountain carving could fit all of Mount Rushmore inside it many times over.

This prehistoric sinkhole lured exclusively male mammoths to their death, much to the delight of science.

A beautiful geyser under environmental threat.

The first declared National Monument in the United States.

Native Americans built this circle of stones, which was used to predict astronomical events.

One man's ambition created this psychedelic log home.

Long before guestbooks and hotels, frontier travelers signed their names on this rock face.

A century-old cabin off of Highway 30 touts an unusual construction material: dinosaur bones.

A popular rock that acted as a waymarker for American pioneers.

Devilish landscape, once cinema home to giant alien bugs, now derelict roadside attraction.

High in the Rockies the third largest statue in the U.S. opens her welcoming arms, and lights up the night sky.

The hill that gave the Massachusett tribe, and later the state, its name.

This beautiful ancient site is dotted with perforated sandstone pillars considered sacred by some Native American groups.

A nostalgic bibliographic gem.

For thousands of years, Native American hunters drove buffalo straight off this cliff in Montana's Yellowstone Country.

The "Seinfeld" diner.

Featuring one of the most complete and original collections of Presidential memorabilia, this is the site of the last front porch presidential campaigns.

The world's first nuclear power plant is open to visitors looking to role-play a meltdown.

This pair of eccentric Ohio castles were built by a pair of brothers who wanted to bring a bit of class to the Ohio wilderness.

The only road through the heart of Glacier National Park.

This record-setting hydraulic dam in the Montana badlands was one of FDR's most ambitious public works.

This Yellowstone geyser may not shoot as high as the nearby Old Faithful, but it erupts for considerably longer.

The only natural lake in the world that drains into both the Atlantic and Pacific Oceans.

An architect's childhood fantasy treehouse made real.