An "acropolis" is simply the high point of the city. This is the acropolis of Corinth. Perhaps because "the Acropolis" has come to mean the one in Athens, this is known as the "acrocorinth."
Rising some 575m above the plane, this is the epitome of "high ground" that you want to take and defend.The hill was fortified even in ancient times, but the walls you see now were constructed, or reconstructed in the 11th cent. (I think.)