Nikolov said the settlement near Provadia was home to some 350 people who likely produced salt from the nearby rock-salt deposits.
"They boiled brine from salt springs in kilns, baked it into bricks, which were then exchanged for other commodities with neighboring tribes," Nikolov said, citing as possible evidence the gold and copper jewellery and artifacts that have been unearthed in the region.
The most valuable is a collection of 3,000 gold pieces unearthed 40 years ago near the Black Sea city of Varna. It is believed to be the oldest gold treasure in the world.
"For millenniums, salt was one of the most valued commodities, salt was the money," Nikolov said adding that this explained the massive stone walls meant to keep the salt safe.
The two-storey houses, as well as the copper needles and pottery found in graves at the site, suggest a community of wealthy people whose likely work was the once-lucrative production of salt.Al Jazeera
Europe's 'oldest town' found in Bulgaria