At the mouth of the river of the same name, the Marismas del Río Palmones Paraje Natural is at the northern end of the Bay of Algeciras (or Bay of Gibraltar depending on your nationality). It is unusual in that it is a Mediterranean estuary with characteristics of the Atlantic.
It is also unusual that it is an unspoilt tidal marismas surrounded by industrial units, oil processing plants and, to the west, the huge port of Algeciras.