My IGN is Handsome Harry
I believe this layout best represents how Athena - the god of war and strategy - would have defended her home city state, Athens.
Athena is said to be able to use Zeus’s bolt of lightning and to carry a shield that, according to some myths, had a Gorgons head in the middle of it. The Gorgon’s head of course had a full head of snakes. She also reared Ericthonius, son of Hephaestus. And he himself was half man and half serpent. Therefore, both lightning and serpent/snake would be incorporated and would play important roles in the defense layout.
According to Wiki, her major symbols include owls, olive trees, snakes, and the Gorgonein, but was also often depicted as holding a spear. These facts then must be taken into consideration when choosing the units to be used.
One of her unique gifts is her wings, which the Griffin is the only unit to have, in addition to also using lightning. So for these reasons it follows that the four units would have to be the Griffin, the Gorgon, the Siren, and the spearmen.
The map’s layout/path is in keeping with the serpent theme and looks like a coiled snake with two Hydra towers at the head of the path representing the serpents head. The parallel paths also make it possible for the Griffin to be able to leap over from one path to the other.
For the reasons and attributes already explained, the maximum number of Apollo and Hydra towers are incorporated into the layout.
According to Wiki: She was believed to have aided the heroes Perseus, Hercules, Bellerophon and Jason. For this reason there are two statues of Hercules fighting serpents near the entrance to the bridge.