South side with walls of the cella (?) visible.
The Parthenon is not the only beautiful building on the Acropolis. Across from the north face of the Parthenon is this building, the Erechtheion. It was built between 421 and 406 B. C. It is named after a mythical Athenian king, Erechtheus, and housed a wooden cult statue of Athena. (Note: there were two other statues of Athena on the Acropolis in ancient times. One was a gigantic gold and ivory statue inside the Parthenon. The other was a 30-foot high statue that stood between the Propylaea, or entrance gate, and the Erechtheion. It showed Athena in armor as the defender of her city. It was said to be so tall that ships at sea could see the shining tip of her spear.) I believe the tree that is visible next to the building represents a sacred olive tree which the ancients believed was a gift from Athena.
The design is not that of a "typical" Greek temple. It is not flat, but is built on two levels, due to its position on the side of a hill. If you stand beside the north wall of the Parthenon this is the view of the Erechtheion you would see. The temple housed the cults of two gods: Athena and Poseidon, plus it was believed to contain the graves of two mythical kings, Erechtehos and Kekrops. This was also considered by Athenians to be the spot where Athena and Poseidon had a fight over who was going to be the patron of Athens. Each offered the Athenians a gift. Athena offered the olive tree, representative of the area's agricultural wealth, and Poseidon offered the sea, with its strategic position along the Aegean trade routes. The Athenians, obviously, picked Athena and so the contest was decided.