Palace-Castle of the Barons Historical milestone · Onil, L'Alcoià, Alicante Image of Onil, not of the place itself. The palace-castle of the barons of Onil was raised at the end of the fifteenth century over an earlier fortress, with courtyard, tower and chapel. It was a seigneurial residence for centuries and today houses municipal offices and collections on local history. siglo XV Photo: José A. Mira (CC BY-SA 3.0) What to see and do in Onil