The Brauronion, located just south of the Propylaia inside the sacred enclosure of the Acropolis, was a shrine dedicated to Brauronian Artemis, protector of women about to give birth and who had just given birth. It probably functioned as an adjunct to the great sanctuary of the goddess at Brauron, Attica. It was founded in the mid-sixth century BC, possibly by Peisistratos, who was originally from the Brauron region.

The main part of the shrine consisted of a Doric pi-shaped stoa, 38 metres long and seven metres wide. The stoa faced north and had ten columns along the fa?ade, while its back wall ran parallel to the southern fortification wall. At either end of the stoa was a closed rectangular wing, 10x7 metres, in which the shrine's treasures were kept. North of the shrine was an enclosure wall with a gate at the northeast corner. The staircase leading to the shrine and the north section of the enclosure wall visible today were built in the fifth century BC, probably during the construction of the Propylaia. The triangular courtyard contained the offerings of the faithful, while the shrine itself probably contained a wooden cult statue of Artemis, similar to the one at the Brauron sanctuary. According to Pausanias, a second statue of the goddess, by sculptor Praxiteles, was placed there in the mid-fourth century BC. The head of this statue is today on display at the Acropolis Museum. A new east wing, consisting of a stoa, seventeen metres long and seven metres wide, was added to the existing one in the fourth century BC.

Today, only the cuts in the bedrock for wall foundations are visible; these allow us to reconstruct the shape and access to the shrine.