This small city where almost everyone lives in the same building can only be reached via North America's longest tunnel.

This WWII-era military installation once held an entire city within its walls - now, its walls are falling down.

At 238 feet above the bottom of a gorge this span is known as the biggest thrill on the road to McCarthy.

Canada shows its hockey pride with a giant stick.

Supposedly Satanic numbers adorn this preserved submarine sail.

Home to the deepest rift anywhere on Earth.

One of nature's most well-scheduled phenomenons resides in Wyoming's Yellowstone National Park.

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

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

The first declared National Monument in the United States.

This shallow pit was once used to send over 20,000 buffalo plummeting to their death.

The highest point in South Dakota contains the ashes of Valentine McGillycuudy, the "Holy White Man."

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

A six-ton, 12-foot-tall concrete prairie dog is touted as the largest in the world.

This simple badlands butte is the highest point in North Dakota and may be the only high point to charge admission.

Inside this museum resides a boot fit for a giant.

Giant six-pack could provide one person a six-pack a day for 3,351 years.

What was once the second largest steel mill in the US is now a sprawling complex of modern ruins.

This castle was once considered as an option for the Royal Family's alternate residence, but you may know it better from the 'X-Men' movie.

An operating lighthouse from the 1860s.

This landmark is a central figure in the Nez Perce origin story.

Derelict buildings are all that remain of a complex at the site of one of the worst mining disasters in Montana history.

An entire city block built completely out of petrified wood.

The world's largest Holstein cow.