The oldest document relating to the Rio Maior salt pans dates back to 1177. Unlike other salt works such as Northwich in England, where the salt is dissolved by adding water & then pumping out the brine, this salt is dissolved in a naturally occurring underground rock salt mine by a natural undercurrent of rain water coming through the hills. This water, seven times saltier than sea water, is fed to a well in the centre of the salt pans. From here is distributed to the salt pans where it evaporates from the warmth of the sun.
Each litre of water holds about 220g of salt.
The salt is then harvested manually and put to dry by the cooperative workers. The area employs about 10- 20 people throughout the year.
The cooperative wooden houses where the salt was ground or bagged for sale are still in place and salt in several forms can be purchased.