Since I'm not sure where you're going with your story/fictional world, this may or may not be relevant:

The Straits of Gibraltar (Gates of Hercules) have opened and closed at various times in the Earth's recent history. When closed, the Mediterranean become a pond and shrinks. This is one reason it's saltier than the Atlantic. Or so it's said. Personally, I have never tasted either.

At times when the Mediterranean is cut off from the Atlantic, water levels go down and vast beds of salt are left behind. There may be salt beds at the bottom of the Mediterranean from the last time it shrank, that have not dissolved again.

Depending on the aims and purposes of your world, you might want to think about how salty the soil of the Mediterranean Valley might be.

--Hugh