Peña de Arcos Nature · Arcos de la Frontera, Sierra de Cádiz, Cádiz Rocky escarpment on which Arcos's historic centre stands, declared a Natural Monument of Andalusia, with views over the Arcos reservoir and the Guadalete river. Photo: Jocelyn Erskine-Kellie from London, UK (CC BY 2.0) What to see and do in Arcos de la Frontera