The ghostly remains of what was once the world's richest copper mine.

A trading post in the North Pole where children send letters.

This frozen tunnel in central Alaska is both an engineering feat and a valuable climate classroom.

The king of U.S. high points towers over every other peak on the continent.

Four-story concrete hotel never opened to customers.

The first declared National Monument in the United States.

A miraculous natural phenomenon known as "the spring that breathes."

One of the largest collections of wildlife art in the United States, built into the side of a cliff in rural Wyoming.

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

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

An architect's childhood fantasy treehouse made real.

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

A beautiful geyser under environmental threat.

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