Arizona-Sonora Desert Museum & Kartchner Caverns

Two unhurried days featuring the Arizona-Sonora Desert Museum and Kartchner Caverns State Park — among the most extraordinary natural history experiences in the Southwest at minimal physical effort. Kartchner Caverns (50 miles southeast of Tucson near Benson) is one of the world's largest and most pristine living caves: 2.5 miles of passages in a limestone cave system discovered in 1974 by spelunkers Gary Tenen and Randy Tufts, kept secret for 14 years while the landowners and state negotiated protection, and opened as an Arizona State Park in 1999. 'Living' means the cave is still actively forming — its stalactites and stalagmites (collectively speleothems) continue to grow because the cave maintains 99% humidity and constant 68°F temperature. The Throne Room tour (one of two cave tours) features the world's longest known soda straw stalactite (21.2 feet) and the Kubla Khan column (58 feet tall). The cave is entirely accessible on paved, lit, wheelchair-accessible paths with a 0.5-mile walking loop.