In southcentral New Mexico, west of Alamagordo, are the world's largest dune fields of gypsum sand. The brilliant white sand dunes cover an area of nearly 230 square miles, with many dunes rising to over 60 feet. The best time to visit Wander far out upon the dunes and spend hours playing and lying in the sand. National Park and government officials will resolutely deny their existence, hundreds of UFO's have been sighted at White Sands during the past 30 years.