Hundreds of almost perfectly preserved artefacts used by native Americans 4,500 years ago have been uncovered in the western US state of Utah.
Many of the objects were found on the ground across the ranch
Granaries, pottery and tools used by Fremont people are scattered along a creek on a ranch located 210km (130 miles) south-east of Salt Lake City.
The sites were kept a secret for over 50 years, in an effort to protect them.
The privately owned ranch has now been turned over to the state of Utah, and will eventually open to visitors.
Although the existence of the sites in a canyon along Range Creek has not been made public until now, archaeologists have been surveying them for the past two years.
Unlike other sites in Utah, Arizona or Colorado, Range Creek has been left virtually untouched.
Many of the artefacts, including human remains, have lain in the same spot since their owners deserted them or died.
"It's a national treasure - there may not be another place like it in the continental 48 states," Duncan Metcalfe, a curator with the Utah Museum of Natural History, told AP news agency.
The Fremont and their ancestors are known to have lived in the area as long ago as 2000BC.
Their population is thought to have peaked between AD900 and AD1100, before apparently disappearing.
Over 220 sites and five villages have already be documented, offering what archaeologists have described as an unspoiled slice of life of the ancestors of modern native American tribes, AP reported.
State archaeologist Kevin Jones said he was elated when he first visited the site two years ago. "You dream of being able to work one site that's undisturbed," he told the Denver Post.
"But to work on a canyon full of undisturbed sites, it's a fantasy.
The rock drawings are extremely well-preserved
"We're all going to retire researching Range Creek," he added.
Arrowheads, pottery shards and other artefacts can still be found lying on the ground. There are hundreds of granaries, some still full of grass seeds and corn.
Rocks used to form half-buried pit houses can still be seen, although their roofs of cedar and soil have long disappeared.
Former owner Waldo Wilcox knew of the remains for at least 50 years before selling the ranch for $2.5m two years ago.
He said he never told anyone about the hundreds of sites to prevent them being stolen.
"I wanted to keep it the way it is," he told the AP news agency.
Mr Wilcox kept looters at bay for over 50 years
He had good reason to be afraid of looters.
Since making the sites' existence known, some arrowheads have disappeared.
"Just outside the gates, there are 8-foot-long and 3-feet-wide trenches where looters dug," Mr Jones told the Rocky Mountain News.
"It's already happening," he added.