The oldest covered railroad bridge still standing in the United States.

Canyon walls shrouded in ferns.

Take a leisurely ride on a 1906 cable car or a 1907 steam locomotive.

The well-preserved remnants of a bridge that once made up a WW1-era military railroad.

Running through lush forests and across the Tadami River, this train line offers breathtaking views of rural Japan.

Outside the Department of Transportation, a collection of artifacts honors the history of how we get around.

This now-abandoned part of the original transcontinental railroad route provides a surreal driving and historical experience.

An excursion train traverses a picturesque red-rock canyon along the Verde River.

Dedicated to one of the nation's worst engineering disasters.

A glimpse into the lives of the the Miwok and Paiute people in Yosemite National Park.

A grove of "candelabra redwoods" deep in California's Lost Coast.

A raised boardwalk winds through a thicket of stunted, century-old trees no more than nine feet tall.

Where NASA's satellites and rovers phone home.

This crumbling Death Valley mining complex was known for its use of giant, 20-mule team wagons.

Curious cave that stays a cool 56 degrees all year long.

This 41,000-acre wetland complex is the largest marsh in the interior of the United States.

America's largest man-made forest was planted in an effort to bring back the past.

The arboretum whose marshy soil sucked up the dreams of housing developers.

A mapping error in the 19th century made loggers think this section of the forest was underwater.

The center of the only hemisphere that awards visitors with a commemorative coin.

Chilly air billows out from the entrance of an abandoned mine on a steep hillside, providing a refuge for Ice Age fauna and flora.

Underneath downtown Lincoln resides a network of caves that was also the city's first brewery.

Nature puts on a spectacular show at this blowhole on the eastern side of Gran Canaria.

Wooden pathways run through this rocky landscape, which legend says was created when a dwarven king pulled down his own castle to stop raiding giants.