Cullera's castle sits high above town, exactly where a fortress should be. The Moors built it in the 10th century, Jaume I took it in the 13th, and later generations adapted it against pirates and 19th-century wars.
The climb is part of the point. The Camino del Calvario zigzags up past stations of the cross, and the reward is a clear view over the beaches, the river mouth, the old town, and the rice country inland.