5. Phoenix, AZ

Downtown Phoenix, shown from atop South Mountain, can be seen sprawling in every direction Wednesday, Sept. 27, 2000. Arizona's Maricopa County, which includes Phoenix and suburbs gained 740,000 residents in the '90s, more than any other county in the nation. Deserts have become developments, highways are clogged and dust cloaks mountaintops, making the region one of the nation's smoggiest. (AP Photo/Matt York)

This sizzling hot city offers the best of both worlds. There are horses, open desserts and picturesque mountain ranges for the nature lover, plus five-star dining, exquisite hotels and eclectic museums for the city slickers.