Nine Mile Canyon is often referred to as the world's longest art gallery.  Located in the state of Utah, the Canyon is five times longer than its name indicates and full of cliffs. But it is also loaded with thousands of ancient images or petroglyphs that go back in time to the mysterious disappearance of a Native American culture.  

At Utah's Nine Mile Canyon, breathtaking views like this one are everywhere.  In this arid environment of cliffs and rocks, there are also thousands of ancient carvings  known as petroglyphs. As a result, the area has become known as the world's longest art gallery.  

"There is a lot of bighorn sheep on this one," Jim Lindsay, the guide at Utah's Natural History Museum points out to visitors. "But there is really no interpretation, I suspect it may be what they call a shadow calendar, which basically uses the circular rings to determine the time of the year," he said.

Ancient cultures etched the petroglyphs in remote places around the world, but never as many over such a large area. Jim and his group of tourists share admiration and curiosity, like many archeologists.

Cherike Lavigne came from Paris says he came, "To discover one of the best places in the United States where you can see Indian petroglyphs," he said.

Nine Mile Canyon, in eastern Utah, is more than 60 kilometers long. Between 1000 and 1250 AD, the canyon was occupied by the Fremont Indians who left evidence of farming and hunting together with images painted on rocks called pictographs -like these - as well as thousands of petroglyphs.  

Then the Fremont disappeared.  Anthropologist Pam Miller is President of the Nine Mile Canyon Coalition. The organization studies and protects the Canyon.  
"There are a lot of theories out there. I think the most mysterious part is what happens to them, around 1250-80, what happened to the Fremont Indians, because we lose them in the archeological record," Miller states.

She says until today, archeologists have documented only about 1,000 rock images, but they estimate there are more than 10,000 in the canyon.

The petroglyphs depict animals and events, like the "Great Hunt Panel." Others include buffalos and longhorn sheep, which are no longer in the region.  Some see abstract forms of deities and demons and even messages.  
"We really don't know what they mean, because we don't have any of their descendants to say our tradition is that, this symbol meant something," Miller said. She adds, religious groups like the Mormons as well as the Ute and Hopi tribes have claimed connections to the region.

Some people see visitors from outer space in the petroglyphs, with aliens wearing antennas, like in the Family Panel.   

"The difficulty about rock art always is that if you have 10 people looking at it you get 10 different interpretations of it," Duncan Metcalfe said. Metcalfe is Curator of Archeology at the Utah Museum of Natural History.  

In 2004, the National Trust for Historic Preservation declared Nine Mile Canyon one of America's most endangered places. It's a patchwork of private and public land.

Vandals used this petroglyph as a gun target. Private owners have written over images, like this one called Rasmussen Site.

Natural gas reserves found in the canyon have brought increased traffic and industrial activity, posing the greatest threat.   

Steve Bloch, of the Southern Utah Wilderness Alliance, says Nine Mile Canyon is an outdoor museum that is being destroyed. "You can still find standing rock art towers from thousands of years ago that withstood the test of time," Bloch said. "But really aren't going to withstand the pressures of natural gas development."

Jim Lindsay says the petroglyphs are in danger. "I predicted that we only have maybe 15, 20 years before they could be so damaged that it would be difficult to see any of them," he said. "The public debate over the extraction of natural gas in the middle of a historic landmark is expected to continue for years to come."