Castellón de la Plana, or simply Castellón, is the capital city of the province of Castellón, in the Valencian Community, Spain. It is locate…Castellón de la Plana, or simply Castellón, is the capital city of the province of Castellón, in the Valencian Community, Spain. It is located in the east of the Iberian Peninsula, on the Costa del Azahar by the Mediterranean Sea. The mountain range known as Desert de les Palmes rises inland north of the town.