Gobekli Tepe is located in southern Turkey near the modern-day city of Urfa. It contains at least 20 stone rings (circles within a circle) that date back more than 11,000 years. T-shaped limestone blocks line the circles and reliefs are carved on them. Long ago, people would fill in the outer circle with debris before building a new circle within. In this photo Professor Tristan Carter is shown alongside one of the rings.

Ancient blades made of volcanic rock that were discovered at what may be the world's oldest temple suggest that the site in Turkey was the hub of a pilgrimage that attracted a cosmopolitan group of people some 11,000 years ago.

The researchers matched up about 130 of the blades, which would have been used as tools, with their source volcanoes, finding people would have come from far and wide to congregate at the ancient temple site, Göbekli Tepe, in southern Turkey. The blades are made of obsidian, a volcanic glass rich with silica, which forms when lava cools quickly.

The research was presented in February at the 7th International Conference on the Chipped and Ground Stone Industries of the Pre-Pottery Neolithic in Barcelona, Spain. [Photos of Göbekli Tepe]

Mysterious temple

Only a tiny portion of Göbekli Tepe has been excavated so far, but what has been unearthed has been hailed by archaeologists as astounding for its great age and artistry.The site contains at least 20 stone rings, one circle built inside another, with diameters ranging from 30 to 100 feet (10 to 30 meters). The researchers suspect people would fill in the outer ring with debris before building a new circle within. [Aerial Photos: Mysterious Stone Structures]

T-shaped limestone blocks line the circles, and at their center are two massive pillars about 18 feet (5.5 m) tall. Statues and reliefs of people and animals were carved on these blocks and pillars. "Some of the stones [the big pillars] are bigger than Stonehenge," said Tristan Carter, one of the obsidian researchers and a professor of anthropology at McMaster University in Hamilton, Canada. (Research on the site has been ongoing since 1994 and is led by Klaus Schmidt of the German Archaeological Institute.)

Even more puzzling is what has not been found. The buildings contain no hearths and the plant and animal remains there show no signs of domestication. Also, so far there have been no buildings found that archaeologists can confirm were used for everyday living.

Taken together, the research indicates the site was created by hunter-gatherers, rather than farmers, who came from across a large area to build and then visit the site for religious purposes. This research is backed up by the style of some of the obsidian and stone tools which suggest that people were coming from Iraq, Iran, the Middle Euphrates and the eastern Mediterranean.

The discoveries made at Göbekli Tepe over the past two decades have led to a great deal of debate. Ted Banning, a professor of anthropology at the University of Toronto in Canada recently published a paper in the journal Current Anthropology arguing that interpretations of the site may be off. Banning suggests the stone-ring structures may have been roofed and used as houses, albeit ones filled with art that may have served as both a domestic space and religious area.He also suggests that the people of Göbekli Tepe could have been growing crops, pointing out that some of the stone tools would have been useful for harvesting and that, at such an early point in history, it is difficult to tell the difference between wild plants and animals and those that humans were trying to domesticate.

Banning told LiveScience that he needs to review the team's latest obsidian results before he can give an informed comment on it.

Volcanic evidence

To try to solve some of the mysteries surrounding the site, Carter's team has used a combination of scientific tests to match up the chemical composition of the artifacts to the volcanoes from which the obsidian originally came.

"The real strength of our work is this incredible specificity; we can say exactly which mountain it comes from, and sometimes even which flank of the volcano," Carter told LiveScience in an interview. [History's Most Destructive Volcanoes]

At least three of the obsidian sources are located in central Turkey, in a region called Cappadocia, which is located nearly 300 miles (500 km) away from Göbekli Tepe. At least three other sources are from the eastern part of the country, close to Lake Van, about 150 miles (250 km) away from the site. Yet another source is located in northeast Turkey, also about 300 miles (500 km).

Researchers say that what make these results special are not so much the distances involved — 300 miles would be a trip from New York City to Buffalo, N.Y., sans any domesticated horses — but rather the sheer variety of obsidian sources used.

"It's an aberration," Carter said. The obsidian finds back up "the idea of many people from many different areas coming to the site," he said.

More mystery

He cautioned that just because some of the obsidian came from such distant sources, that doesn't mean that people were actually travelling directly from these regions to Göbekli Tepe. The obsidian may have been acquired by way of trade, turned into a tool, and then brought to the site.

To try to resolve this problem, the team is also looking at the way the obsidian tools were made. For example, they found that obsidian artifacts sourced to Cappadocia, in central Turkey, tend to be stylistically similar to artifacts found to the south of Göbekli Tepe in the Middle Euphrates region of Mesopotamia. Also some of the obsidian artifacts sourced to eastern Turkey, the Lake Van region, have similarities to those made in Iraq and Iran. Altogether, these finds suggest that some of the obsidian made its way south and east (possibly through trade) before it was turned into tools and brought to the site, another clue as to where people were coming from.

Though more research is needed to make any conclusive statements, if the team is right, then Göbekli Tepe was indeed something grand, a place of pilgrimage more than 11,000 years old that attracted people from across the region.

"If Professor Schmidt is correct, this represents a very cosmopolitan area, this is almost the nodal point of the Near East," Carter said. "In theory, you could have people with different languages, very different cultures, coming together."

The obsidian samples were analyzed at facilities at the Musée du Louvre in Paris and McMaster University. In addition to Carter and Schmidt, the team includes François-Xavier Le Bourdonnec and Gérard Poupeau of the Centre National de la Recherche Scientifique.