SOFIA, Bulgaria (AP) — A Bulgarian archaeologist says a prehistoric town unearthed in eastern Bulgaria is the oldest urban settlement found to date in Europe.

According to Vasil Nikolov, a professor from Bulgaria’s National Institute of Archaeology, the stone walls excavated by his team near the town of Provadia are estimated to date between 4,700 and 4,200 B.C.

He says the walls, which are 3 meters (6 feet) high and 2 meters (4 1/2 feet) thick, are believed to be the earliest and most massive fortifications from Europe’s prehistory.

According to Nikolov, the settlement was home to some 350 people who likely mined salt at the nearby rock-salt deposits. Samples of the excavations have been sent to scientific centers abroad for further evaluation.