A beautiful geyser under environmental threat.

The first declared National Monument in the United States.

Look closely and you’ll notice that the color changes a third of the way up the tower.

An overlooked memorial honoring the local Washington residents who died in World War I.

The highest point in Washington state is a volcano covered in glaciers.

A wall of chewing gum moonlights as collective art.

The marker offers a rare chance to be in four U.S. states at once, though there's some controversy over its geographic accuracy.

Giant, natural amphitheaters made of delicate geological formations called "hoodoos."

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

A vertically floating hemlock controls the waves and weather at Crater Lake.

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

A terrific purveyor of natural history objects and curios.

The oldest operating apothecary in the US has treated everyone from Thomas Edison to Mark Twain.

This exemplar of modernist architecture is meant to captivate and inspire students of the Cooper Union.

A semi-scholarly approach to sex.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

The only road through the heart of Glacier National Park.

The massive machine creates cracking displays of indoor lightning.

This monument on Breed's Hill proves that one of the most famous battles of the Revolutionary War is misnamed.

Berthed at the Charlestown Navy Yard in Boston, "Old Ironsides" is the oldest commissioned warship still afloat.

One of the most scenic falls in Massachusetts has a history of death and grim legend.

The world's longest known cave system.

First a horse rendering plant, then a 19th century landfill, this beach is full of glass from thousands upon thousands of broken bottles.

Home to the deepest rift anywhere on Earth.