Frozen on stone for centuries, the larger-than-life cave paintings of humans and animals in Baja's Sierra de San Francisco hover over the thousand or more awe-struck visitors who come to see them in a typical year. My opportunity to visit the remote mountain range -- 500 miles down Baja's skinny peninsula -- and to view several of the finer pictograph sites came last April, during an agreeably warm spell. Cirrus clouds painted the sky with ever-changing patterns most of the time, preventing peak temperatures from rising much higher than 90 degrees. In addition to mid-spring, the following few weeks (mid-September through November) should be ideal for visiting the area.

Make no mistake: the trek is hardly a casual one. The approach by car involves some 500 miles of travel on Baja's main arterial highway. In places, the highway is merely a narrow strip of asphalt barely wider than the width of two large trucks. The often unguarded road shoulders are littered with the carcasses of vehicles and livestock and are decorated with shrines to the highway's many human victims. From the highway, a 25-mile journey over an unpaved road coated with suspension-busting rocks takes you to the isolated mountain villages of Rancho San Francisco de Sierra and Rancho Guadalupe. There, by virtue of necessary arrangements made earlier in the town of San Ignacio, you join local guides for the day-long trek by foot down into the canyon system harboring the better-known pictograph galleries.

Our group of five hired two guides, who rode mules over the perilous terrain. We also arranged for the use of five burros (donkeys) to carry camping gear. Of these five, four returned; one suffered a near-fatal attack by a mountain lion while foraging for food near our campsite and had to be destroyed.

Two full days suffice for side trips from the main canyon-bottom campsite to the four or five most noted pictograph-decorated overhangs, or cuevas (caves). These include Cueva Flechas, where the two-dimensional and static figures of humans produced with red and black mineral pigments compete for space with the more dynamic images of various animals. Many of the figures here are pierced with black arrows. Cueva Pintadas, a dramatic horizontal rift in the canyon wall, features a jumbled array of human and animal (terrestrial, aerial, and aquatic) figures stretching some 500 feet. The paintings attain heights of 20 feet or more from the nearest flat ground. Who painted them? Local legend says "giants from the north." A more rational explanation would be former indigenous people associated culturally with the Anasazi of the American Southwest.

With help from the Getty Museum, Mexican authorities have installed walkways and railings at the main sites that keep tourists from damaging the precious artwork. Local guides must be present during all visits. A good review of the logistical aspects of traveling to and visiting the Sierra de San Francisco appeared in the February 20, 2000, "Sunday Travel" section of the San Diego Union-Tribune. Much information is also available on the Internet (use the keywords "Baja cave paintings"). Anyone serious about the subject will want to purchase the recently revised book The Cave Paintings of Baja California by Harry Crosby.