Río Biobío
On the other hand, Spanish chroniclers Miguel de Olavarría and Diego de Rosales claimed instead the Inca frontier lay much more to the south at the Bío Bío River. Regardless of these differing claims on the frontier of the Inca Empire, Inca troops appear to have never crossed Bío Bío River. As in the case in the other borders of the Inca Empire, the southern border was composed of multiple zones. First an inner fully incorporated zone with mitimaes protected by a line of pukaras (fortresses) and then an outer zone with Inca pukaras scattered among allied tribes. This outer zone would have been located between Maipo and Maule rivers.