American researchers have discovered what they say is the world's oldest paved road: a 4,600-year-old highway that linked a basalt quarry in a desolate, deserted region of the Egyptian desert to waterways that carried basalt blocks to monument sites along the Nile. The eight-mile-long road is at least 500 years older than any previously discovered road and is the only paved road discovered in ancient Egypt, said geologist Thomas Bown of the U.S. Geological Survey in Denver, who will report the discovery Friday at a regional meeting of the Geological Society of America in Durango, Colo. "The road probably doesn't rank with the pyramids as a construction feat, but it is a major engineering achievement," said his colleague, geologist James Harrell of the University of Toledo in Ohio. "Not only is the road earlier than we thought possible, we didn't even think they built roads."

The researchers made an additional discovery in the quarry at the northern end of the road, the first evidence that the Egyptians used rock saws for cutting the basalt into blocks. "This is the oldest example of saws being used for cutting stone," said archaeologist James K. Hoffmeier of Wheaton College in Illinois. "That's two technologies we didn't know they had," Harrell said in a telephone interview. "And we don't know why they were both abandoned." The road was discovered in the Faiyum Depression, a low area about 45 miles southwest of Cairo. Short segments of the road had been observed by earlier explorers of the area, Bown said, but they failed to realize its significance or to follow up on their observations. Bown and his colleagues stumbled across it accidentally while they were doing geological mapping in the region. The road was clearly built to serve the newly discovered quarry, where the heavy black basalt was laid down by volcanic eruptions about 30 million years ago. Bown and Harrell have found the camp that housed the workers at the quarry, and numerous pottery sherds and artifacts date the site to the Egyptian "Old Kingdom," which began about 2600 B.C. The road appears today to go nowhere, ending in the middle of the parched desert. When it was built, however, its terminus was a quay on the shore of Lake Moeris, which had an elevation of about 66 feet above sea level, the same as the quay. Birket Qarun, the lake that is now at the bottom of the depression, has a surface elevation of 148 feet below sea level, reflecting the sharp change in climate in the region. Lake Moeris received its water from the annual floods of the Nile River. At the time of the floods, the river and lake were at the same level and connected through a gap in the hills near the modern villages of el-Lahun and Hawara. Harrell and Bown believe basalt blocks were loaded onto barges during the dry season, then floated over to the Nile during the floods to be shipped off to the monument sites at Giza and Saqqara. The road was constructed with flagstones, large slabs of stone that were laid on the sand without any surface preparation. The nature of the stones varies according to location on the road. "It's clear they just used whatever was handy," Bown said. The road is a little over six feet wide -- "almost exactly four cubits," Bown said. Although the main road is just under eight miles long, branches at the quarry bring the total to about 11 miles.