Along the coast of Malta, you often find stone pans carved into the rock, from the time of former salt production - some of them up to 350 years old. The Mediterranean has with > 38 ppt a very high salinity, given high evaporation, low rainfall and being except the Gibraltar strait cut off from the Atlantic. But I guess, the main reason why they exist is not the salt content of the sea water, but the need for Maltese to take any business opportunity and no other significant resources on the island. The salt pans pictured below, are no special ones, but just a structure you find walking South of Fort Rinella - here taken on the New Year Walk 2017. Of course, now is not "salt season", but in the hot summers.