Bulgaria’s Provadiya Had Oldest Stone Fortress Walls in Europe dated 6700 years old
Some 6,700 years ago the residents of the Solnitsata (“The Salt Pit”) prehistoric town in today’s Provadiya in Northeast Bulgaria built what were Europe’s first fortress walls made of stone in order to protect their riches accumulated from the large-scale production of salt extracted from a massive rock salt deposit.
Novinite.com