The flow from this waterfall sometimes comes out of springs below its rim.

The first radio telescope dedicated to the Search for Extraterrestrial Intelligence.

A large lava tube that can be walked through with no special equipment.

Sunset-colored dunes of volcanic ash make taking a poor photo impossible.

This ultra-modern California span is actually a titanic solar clock in disguise built by famed architect Santiago Calatrava.

One of the most scenic stretches of road in America winds between some of the country's oldest trees.

A vaudeville performer mounted this hollowed-out redwood log onto the chassis of a truck, and toured the country spreading a message of conservation.

Commonly referred to as the most photographed Victorian home in the United States.

Canyon walls shrouded in ferns.

These cinderblock farmhouses were actually World War II radar stations in disguise.

This 19th-century museum inside of a lighthouse is only accessible during low tide.

The deepest lake in the United States, and once the site of epic destruction that lives on in legends.

Limestone caves with spectacular showcase chambers.

America's only nuclear missile silo open to the public.

See massive fossils that are over 200 million years old in northeastern Arizona.

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

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

The museum is housed inside the historic 1863 Carson City Mint.

A granite primate with a view.

The drama of nature in full effect in this Nevada State Park.

The last remnant of a tree that helped prove to the world that sequoias are real—and they’re spectacular.

The second-largest giant sequoia in the world.

This hidden fire lookout offers spectacular views of Sequoia National Park.

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