Dominating a curvaceous promontory over the Río San Pedro, this crumbling 12th-century pukará (fort) was one of the last bastions against Pedro de Valdivia and the Spanish in northern Chile. The indigenous forces fought bravely, but were overcome and many were promptly beheaded. About 100 defensive enclosures hug the slopes here, like big stone bird's nests. The hilltop commands an impressive view of the oasis.
The fort is just 3.5km northwest of San Pedro, and easily accessible on foot, by bike or by vehicle. Note that the mirador (lookout) closes at 6pm.