Arcos de la Frontera (ärˈkōs dā lä frōntāˈrä) [key], town (1990 pop. 27,722), Cádiz prov., S Spain, in Andalusia, on a rocky hill above the Guadalete River. A Gothic church and the palace of the duke of Arcos are at the summit. Wine and olive oil are produced. The Moors were driven out in 1250, and it became a Christian town near the border with Muslim Spain.