Substantial cultural changes become evident during the Late Formative, including a dramatic population shift and the political centralization of the valley under the previously uninhabited capital of Monte Alban. There is no evidence that Monte Alban existed as of 600 BC, but by 400 BC the site, which is located atop a 400 m tall artificially leveled mountain and completely lacking in easily accessible water sources, had a population of ca. 5,200. Within 200 years, the settlement’s population had grown to approximately 17,200, quickly making it one of the most populous Mesoamerican cities at the time. This inordinate population growth occurred simultaneously with the rapid abandonment of the other major centers occupying the three arms of the Oaxaca Valley (San José Mogote, Tilcajete, and Yegüih). The rapid shift in population and settlement, from dispersed localized centers to a concentration in a previously unsettled area, has been referred to as the “Monte Alban Synoikism” by Marcus and Flannery.