Some time during the Classic period, a Monte Albán ruler called 12 Jaguar came to power and dedicated a huge platform on the southern side of the the Main Plaza. To commemorate the event, several stelae were located at the corners of the platform. Buried under these stelae were found a variety of offering boxes and jars containing shells and jade beads.
One of the corner stela, Stela 1, portrays the ruler 12 Jaguar sitting on a bench throne with in front a series of glyphic inscription referring to his divine origins and deeds. The other stelae portray bound captives possibly sacrificed during the dedication ceremony.
The southern platform is a massive structure, measuring about 400 ft on the side. On its top are two pyramidal structures separated by a patio. The top of the platform can be reached from the main plaza by an imposing stairway.
During the Postclassic period, a defensive wall was constructed along the northern edge of the platform.