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

A beautiful geyser under environmental threat.

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

An architect's childhood fantasy treehouse made real.

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.

Home to the deepest rift anywhere on Earth.

A psychedelic labyrinth on the San Francisco bay.

This reclusive Hopi village in Arizona has been continuously populated longer than anywhere else in America.

Ancestral Puebloan ruins, natural arches, and box canyons abound in this seldom-visited corner of Monument Valley Navajo Tribal Park.

Contrary to what one might expect, ice forms inside this small cavern during the summer and melts during the winter.

Once the "Eighth Wonder of the World," this iron railroad bridge was decimated by a tornado.

The artist James Turrell is repurposing an extinct volcano crater as an observatory to experience the cosmos.

The highest point in Arizona is an oddly snow-topped peak within the otherwise arid state.

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

Home to a protest movement, a bombing, and a dramatic change in labor history.

Once called the "Polish Gold Coast" it is an icon of the neighborhood that bears its same name.

A European-style bath house in Chicago.

The unluckiest U-boat in the entire German fleet is now on display in a Chicago museum.

Kentucky's anomalous peninsula projecting into the Mississippi River, site of legendary earthquakes and local feuds.

This art deco masterpiece was once a miracle spring mecca but is now simply a government office building.

River pirates, murderous bandits, and serial killers used this Illinois cave as their debauched hideout.

European castle ruins in an American state park are actually the product of death and grief.

A notorious Route 66 eatery once frequented by Al Capone.