The ancient little town of Alcácer do Sal ("castle of salt"), the Roman Salacia, lies above the right bank of the Rio Sado, which here opens out into a wide estuary. The banks of the river are lined with the salt-pans which have given the town its name. A number of fine old buildings bear witness to the
town's earlier prosperity, achieved from medieval times onwards by its flourishing trade in salt and corn, and the growing of rice in the warm low lying marshland along the river, a crop that has increased in importance since recent decades have seen many of the salt-pans around the town abandoned.