Ancient ruins of Canyon de Chelly: Centuries ago, people built shelters into the canyon's walls, taking advantage of ledges and overhangs. The largest and most impressive is the White House Ruin, a multilevel structure that likely served as an ancient condominium. Navajo people still live and work in the canyon, and visitors must arrange for a guided tour to enter the canyon (highly recommended, because only then can you see and appreciate the many ruins and pictographs carved into the walls). 
Details: www.nps.gov/cach  

Hoover Dam: It took five years, $49 million and 4.4 million cubic yards of concrete to build - how wondrous is that? The dam, begun in 1931, straddles the Arizona-Nevada border, so in a geographic sense, it is only half Arizona's. Even at that, it's still a wonder. You must take a tour to really appreciate it (the visitor's center is in Nevada for those keeping score). The most awe-inspiring view is from the base of the dam where its 726-foot height is overwhelming. 
 Details: www.usbr.gov/ lc/hooverdam 

Montezuma Castle National Monument: It may have been drought or, perhaps, invaders; no one is quite sure why the original inhabitants abandoned this impressive high-rise roughly three centuries after it was built in 1100. Montezuma Castle is one of the best-preserved cliff dwellings in North America. It is easy to imagine people still living amid its 20 rooms. No wonder when President Theodore Roosevelt celebrated the passage of the Antiquities Act in 1906, he declared Montezuma Castle as one of four national monuments. 
 Details: nps.gov/moca 

Lowell Observatory: The familiar dome of the observatory greets visitors to this Flagstaff wonder. Percival Lowell founded the observatory in 1894, a time when light pollution referred to the smoke coming from the whale-oil lamp. Open for tours and occasional astronomical viewings, Lowell Observatory is best known for the part it played in the discovery of Pluto, the solar system's most famous ball of ice. Pluto, considered a planet for decades, was spotted by astronomer Clyde Tombaugh in 1930.
 Details: www.lowell.edu

University of Phoenix Stadium: No surprise this Glendale stadium with the geographically challenged name made the list. The stadium's otherworldly look only adds to its architectural mystique. Still, with a retractable field and energy-conserving features, it is state of the art in terms of football stadiums, and will be shown off to the world as host of next year's Super Bowl. 
 Details: www.universityof phoenixstadium.com

Chapel of the Holy Cross: Even the not very religious turn off the highway in Sedona to get a close look at this small church perched delicately amid the red rocks. Take a seat in the pews and admire the view through the immense picture windows behind the altar. Then head to the patio for an even better look at the area's stunning rock formations. Finished in 1956, Chapel of the Holy Cross sits atop a pinnacle 250 feet above the valley floor. The chapel blends in with its surroundings, looking almost as if it was a natural formation. It was designed by architect and sculptor Marguerite Brunswig Staude. 
 Details: www.chapelofthe holycross.com

London Bridge: Critics thought chain-saw tycoon Robert McCulloch had a little buzz on the brain when he bid $2.4 million for the London Bridge in 1968. The stone bridge was slowly sinking into the Thames River when the city of London put it up for bid. (This was way before eBay). McCulloch thought it would be just the thing to rev up interest in Lake Havasu City, which he founded. McCulloch spent another $7 million transporting the bridge, stone-by-stone from England and reassembling it in the desert, where it now spans a small channel dredged from Lake Havasu. It opened in 1971.
 Details: golakehavasu.com