Explore Swiss-cheese rock at Mojave National Preserve's Hole-in-the-Wall recreation site.

East Mojave National Preserve, a vast, empty sprawl of desert sand, alkali flats, cinder cones, and skeletal mountains, lies wedged between Interstates 15 and 40 east of Barstow, south of Baker, and west of the California-Nevada boundary. Smack-dab in the middle of this 1.4-million-acre preserve lies Hole-in-the-Wall, a recreational site containing a campground, a visitors' center, and enough "Swiss cheese" rock formations to keep any kid (of any age) busy exploring for hours.

At 4200 feet elevation, Hole-in-the-Wall is perfectly serene and warm on calm, sunny days during March and April, but chilly whenever a late Pacific storm passes by, bringing clouds and blustery winds. The clear days are usually followed by clear nights. If those are moonless nights as well, then the stars over Hole-in-the-Wall shine brighter than they do anywhere in San Diego County. The only significant source of artificial light is Las Vegas, about 70 miles away. Evening skies will be moon free in late March through early April and again in late April through early May.

San Diegans should allow a minimum of five hours for driving to Hole-in-the-Wall. Take I-15 north to Barstow, then take I-40 east for 99 miles to Essex Road. Go north on Essex Road for 9 miles to Black Canyon Road, and continue north on Black Canyon Road another 9 miles to Hole-in-the-Wall. The entire route is now paved.

The bold and vaguely grotesque rock outcrops at Hole-in-the-Wall are made of volcanic breccia, which is easily weathered and eroded by wind and water. At one spot, the wall to the west of the campground is breached by a steep, narrow passage leading down to a spooky amphitheater called Banshee Canyon. Iron rings set in the rock assist climbers on the descent and ascent.

In nearby Wildhorse Canyon, some two miles from Hole-in-the-Wall, another tortured outcrop of volcanic rock rises from the sandy desert floor. Amid the heap of boulders at its base are inscriptions made by long-departed Native Americans. Above the fading petroglyphs and pictographs is a round aperture through which (it seems) generations of Indians slid through in symbolic acts of rebirth. The rock itself is worn glassy smooth from thousands of birth passages. Formerly, a primitive road passed near this site, but now it's necessary to walk some distance to reach it.

For further information about Hole-in-the-Wall, or Mojave National Preserve, call 760-733-4040.