A place where salt was produced by evaporating the water from brine to leave crystalline salt blocks. In northern Europe most salterns are situated on the coast and comprise a series of large open tanks that could be flooded with a controlled amount of seawater at high tide before being closed off to allow natural evaporation to concentrate the solution. When the brine in the open tanks was sufficiently salt‐rich it would be taken to smaller tanks that could be heated by fires underneath in order to be further concentrated. In later prehistoric and Romano‐British times, highly concentrated salt water would be placed in ceramic containers (briquetage) for final reduction and drying in purpose‐built hearths. Inland, salterns are also found around saline springs such as in Cheshire, England.
Archaeologically salterns can be identified by the earthwork remains of the preliminary evaporation tanks and the extensive areas of burning associated with the reducing hearths. In Essex, England, these areas of burning have become known as ‘red hills’.