Archaeologists have uncovered what they believe to be Europe’s most prehistoric town, dating back between 4,700 and 4,200 B.C.

The archaeologists found the remains of the ancient settlement, including the ruins of two-story houses, fortification walls and parts of a gate near the modern-day town of Provadia.

The town dates back to more than a millennium before the start of Greece’s ancient civilization.

Stone walls excavated by the team are 6-feet high and 4.5-feet thick, and they are believed to be the earliest and most massive fortifications from Europe’s prehistory.

Experts believe the townspeople likely mined salt at the nearby rock-salt deposits, which was probably the reason for their settling

The inhabitants of the ancient settlement boiled brine from salt springs in kilns, then baked it into bricks and used it for trading. This could explain why ancient caches of gold jewelry and ritual objects have been unearthed in the area.

Nearly 40 years ago, archaeologists unearthed a collection of 3,000 gold objects at a necropolis near Varna.

“At a time when people did not know the wheel and cart, these people hauled huge rocks and built massive walls. Why? What did they hide behind them? The answer was salt,” Vasil Nikolov, a researcher with Bulgaria’s National Institute of Archeology, told AFP.

“Salt was an extremely valued commodity in ancient times, as it was both necessary for people’s lives and was used as a method of trade and currency starting from the sixth millennium BC up to 600 BC,” he said.

The settlement, known as Provadia-Solnitsata, was small, and would have had about 350 inhabitants during its time.

“We are not talking about a town like the Greek city-states, ancient Rome or medieval settlements, but about what archaeologists agree constituted a town in the fifth millennium BC,” Nikolov told AFP.

Samples of the excavations have been sent to scientific centers in other countries for further evaluation.