READERS' PICK: Standing on a corner in Tucson, Arizona ... the name means "Desert Corner" in O'odham, and once upon a time the little patch of desert that is Tohono Chul Park stood in a quiet, unexplored nook of Tucson's northwest side. Now surrounded by the asphalt jungle, the park--a dense forest of saguaros, cholla, Spanish bayonet and other native plants--is a haven for cacti lovers everywhere. A recently completed facelift has brought new greenhouses and a garden shop to the park--and, for the first time in the park's two-decade history, an entrance fee, a matter of five bucks for nonmembers. But what better cause than an island of beauty in the wasteland that our once-fair city has become? Pay up and enjoy one of the Old Pueblo's true treasures.