For all I could read up this is one of some (huge) Medusa heads near the ticket office.
From the Enc. Britt.: in Greek mythology, the most famous of the monster figures known as Gorgons. She was usually represented as a winged female creature having a head of hair consisting of snakes. Unlike the other Gorgons, she was sometimes represented as very beautiful. Medusa was the only Gorgon who was mortal; hence her slayer, Perseus, was able to kill her by cutting off her head. From the blood that spurted from her neck sprang Chrysaor and Pegasus, her two sons by Poseidon. The severed head, which had the power ofturning into stone all who looked upon it, was given to Athena, who placed it in her shield; according to another account, Perseus buried it in the marketplace of Argos.