On the northern edge of Tucson, you can drive through a condensed version of western North America's ecosystem in about half an hour. On the way up the Mount Lemmon Highway (also known as "Catalina Highway" or "Sky Island Scenic Byway"), you traverse almost all of the different life zones you would encounter if you were to actually drive from Mexico to Canada: starting with the saguaro-studded Sonoran desert, up through grassland, junipers and oaks, pines, and finally a mixed-conifer forest with stands of aspen.
You begin at about 2500 ft. and end up at almost 9100 ft. above sea level (about 760 to 2770 meters).
In the summer, especially, southern Arizonans love this road: "thirty miles, thirty degrees cooler," as the saying goes. When it's 105 degrees down in the city, it's a perfect 75 up on the mountain. In the winter, you can go skiing in the southernmost ski resort in the U.S.