Castell de Polpís is a rougher, quieter companion to Peñíscola's famous sea castle. The ruins sit inland on a hill above Santa Magdalena de Polpís, with broken walls, scrubby paths, and wide views that remind you how many small fortifications once guarded this coast.
Come for the walk and the setting rather than a restored monument. It makes a good half-day escape when Peñíscola's old town is crowded, especially if you want a little history without ticket queues or polished interpretation panels.