This vast quadrilateral (400m sides) was Teotihuacán's centre of political and religious power. It did not play a defensive role, its Spanish name of "citadel" notwithstanding. The large low-lying platform (patio escondido) is laid out like an esplanade, perhaps for ritual dances. The fifteen foundations of ancient temples surrounding it are an example of talud-tablero construction alternating slopes and vertical walls. The Temple of Quetzalcóatl was flanked by residential areas on both sides.