Leave These Southwest Ruins Alone WATERTOWN, Mass. - IT has been called the best preserved ruin in the Southwest. Built in the 13th century by Ancestral Puebloans, its 20-odd rooms splendidly fill an oval sandstone alcove in an obscure canyon on the Navajo reservation in Arizona. When I visited the place in 2009, official permit in hand, I was content to admire the ruin through binoculars from the opposite rim and from the creek bed at its base, for the Navajo Nation forbids all access to the site. When I wrote about it, I described its location no more precisely than I have here. If you know the name of the ruin, however, you can go on the Internet and instantly find the GPS coordinates that tell you exactly where this prehistoric wonder lies. You can also open a Flickr photo of a fellow using a climbing rope to get into the ruin, and bragging about doing so. Only one of the web postings I checked out mentioned the prohibition against entering the site or the permit needed to hike the canyon - that of the Navajo Nation itself. The ruins and rock art left behind by the Old Ones all over the Southwest constitute, arguably, our country's richest archaeological heritage. And they stand as mute testimony to a profound mystery - the sudden abandonment by the Ancestral Puebloans (also known as the Anasazi) of the whole of the Colorado Plateau in the years just before the beginning of the 14th century. Many of the places where the Ancestral Puebloans once flourished are not only uninhabited today; they are so remote that it can take several days of backpacking through trail-less, tortuous canyons to reach them. Scattered about these ruins still lie broken pieces of painted pottery, chert flakes from which stone tools were made and corncobs filling granaries where the last dwellers left them. Under the dirt sleep the dead who made this world cohere. Yet no prehistoric sites in the United States are more fragile and vulnerable. A century and a half of looting and vandalism has severely damaged such monumental villages as Cliff Palace at Mesa Verde and the cave dwellings of Bandelier National Monument. By now, all that saves the still-pristine sites such as the one on the Navajo reservation is their obscurity and the difficulty of getting to them. With my fellow aficionados of the canyon country, I adhere to a rigid ethic: When you visit the ruins and rock art, disturb nothing, and if you write about them, be deliberately vague about where they are. In the last 10 years, however, a rash of guidebooks, with titles such as "Hiking From Here to WOW: Utah Canyon Country," serve up detailed directions to some of the finest but still little-known sites. The most ominous new trend is the proliferation of websites giving the GPS coordinates of those prehistoric ruins and rock art panels. Armed with those numbers, the most casual curiosity seeker need not even read a map: One can simply home in on the place with device in hand. And it is those folks, I believe, like the climber on Flickr with the self-portrait of his illegal climb into the forbidden ruin, who are most likely to take home potsherds or arrowheads as souvenirs, or to damage the stone-and-adobe rooms as they clamber through them. Can anything be done to reverse this trend? Americans are as fond of gizmos like the GPS as they are of guns. The Navajo Nation cannot be expected to post a year-round guard at that matchless ruin in the obscure canyon or at others in the remote reaches of the reservation. And government agencies cannot police the thousands of sites on federal land all over the Southwest. Educating the public may be the only hope. We can take heart in the virtual disappearance of some of the more rapacious crimes against Southwestern prehistory. In the early decades of the 20th century, for instance, ranchers and locals made a sport of using the petroglyphs for target practice. Their bullet scars are as indelible as the surreal humanoids carved so long ago into the sandstone. To their credit, most of the recent guidebooks include codices about visitation etiquette. But not so the GPS postings on the web, which exude only a hearty "Hey, check this out!" tone. As I've seen all too often when other people showed up at a ruin or rock art panel I was admiring, the ones who know the least about the ancients are the ones most likely to yank on fragile walls for handholds or stick artifacts in their pockets. And not a few of them consult their GPS devices to make sure they've truly arrived. David Roberts is the author of books about adventure and Western history, including "In Search of the Old Ones."