Originally conceived as part of a proposed Arizona State Capitol building in the 1950s, this structure built in 2004 stands as a monument to the architect's legacy.

The largest natural travertine bridge in the world is nestled in a small canyon in central Arizona.

Aqueducts have dramatically changed this old lake, now home to tufa towers and its very own species of tiny brine shrimp.

The now-abandoned tunnels were built for the transcontinental railroad on the route where the first wagon train entered California.

A classic Route 66 landmark that was built with scrap lumber and is held together with kitsch and puns.

A small canyon with petroglyphs and a seasonal waterfall, only a short hike from the remnants of old Route 66.

Every year, festive decorations appear on this juniper tree located in the median strip of a busy highway.

This sinkhole in the Arizona desert is filled with carbonated, arsenic-rich water

The first of the iconic American roadside attractions lives on as a college mascot.

Crafted in 1911, this steam locomotive spent its entire working life in Flagstaff.

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

A planet-hunting astrograph built in the 1920s to seek out the so-called "Planet X" beyond Uranus.

A replica of the flagpole that gave a frontier town its name.

This 1930s log cabin began as a taxidermy museum but is now a popular country music venue.

A nature and cultural preserve named for its multitude of petroglyphs carved by the Northern Sinagua people.

This historic national park is covered in the stunning ruins of red rock pueblos.

At 11,500 feet in elevation, there is no toilet in the state closer to the sky than this one.

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

Eons ago, a rushing lava river formed this pristine passage through solid rock.

The eroded core of an ancient volcano is now accessible by a short hike.

This set of three large, volcanic hot springs is a favorite haunt for intrepid divers.

One man has installed bathtubs into the Utah desert floor to harness the powers of a natural hot spring.

An arsenic-filled pool in the Grand Canyon takes on the appearance of a giant, overflowing pumpkin.

This secluded aqua waterfall in the Grand Canyon is the perfect swimming hole, and the Havasupai tribe's fiercely protected natural wonder.