At a rest stop north of Seattle, the trunk of an ancient tree.

This magnificent natural sandstone bridge is one of the largest in the world and is an iconic symbol for Lake Powell.

The damming of the Colorado River buried an iconic geologic formation before record-breaking drought brought it back.

Archaeologists believe this panel of petroglyphs depicting descending sheep and other figures in Glen Canyon are 3,000 to 6,000 years old.

When it was built in 1929, this historic bridge was the only place to cross the Colorado River for 600 miles.

The beloved, war-tested mascot of a Union regiment graces their battlefield monument.

A granite monument honors a beloved World War II canine mascot.

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

The hidden offices underneath Memorial Bridge have been locked up since 1976.

Cross the Continental Divide through an old railroad tunnel, and ride back to the top on a shuttle.

For decades, it has disappeared and reappeared as water levels rise and fall.

An abandoned railroad tunnel transformed into a creepy path for hikers and cyclists.

Once a sewer culvert, this road tunnel now offers cyclists and pedestrians a subterranean stroll under the C&O Canal.

This forgotten boat elevator was an engineering marvel in its heyday.

This isolated outpost was once the only place to cross the Colorado River for hundreds of miles.

This unique art installation used boiler tubes from a decommissioned power plant to resemble Antelope Canyon.

Dramatic river bend surrounds a natural red-rocked pedestal.

This hidden gem in Arizona is truly worth the rugged journey.

This beautiful ancient site is dotted with perforated sandstone pillars considered sacred by some Native American groups.

The Old Man of the Mountain’s less-famous, but still beloved little brother is said to resemble a leader of the Abenaki tribe.

Come for the gun-toting hillbilly madman, stay for the ice-cream loving basketball bears.

Even Henry David Thoreau found this glacial pothole irresistible.

A serene plaza that commemorates one of the Granite State's most iconic figures.

Some believe this tree to be more than 1,500 years old.