In the vicinity of the Propylaea was the sanctuary of Artemis Brauronia, whose construction dates back to 430 BC. The story behind this sanctuary is based on a legend that the inhabitants of Brauronia had hunted and killed a bear, the sacred animal of Artemis. In response, the goddess demanded that girls between the ages of seven and eleven, who would live in the sanctuary to serve Artemis and were known as "bears", be consecrated to the cult. The building had a trapezoidal layout with two lateral wings and a stoa measuring about 38 meters long by 7 meters wide.
Pausanias describes several statues that were in this sanctuary, including a representation of Artemis created by Praxiteles and a bronze horse symbolizing the Trojan horse. This bronze horse showed some of the warriors hidden inside, peeking out from within.