White Sands National Park, about 80 kilometres east of Las Cruces via US-70, is the region's single greatest natural attraction and one of the most extraordinary landscapes in North America. The gypsum dune field stretches for miles in every direction, bright white and shifting, with no vegetation except for a few hardy species that have evolved specifically for this environment. Walking into the dunes feels like entering another planet.
The park has several hiking trails ranging from a boardwalk interpretive loop (excellent for children) to the Alkali Flat Trail, a 8-kilometre round trip into the remote dune field. Sledding on the dunes is a popular activity — plastic sleds are sold at the visitor centre. Sunset is spectacular, and the park is open for a couple of hours after dark on most evenings for stargazing; the dune field under a full moon is one of the more magical experiences in the Southwest.
Be aware that the park sits within White Sands Missile Range, and US-70 through the dune field is occasionally closed for missile testing. Check the park website before going, as closures happen without much advance notice and can last several hours. The visitor centre is worth stopping at for the exhibits on how the gypsum dunes formed.