The hilltop Castillo de Monfragüe, a ruined 9th-century Islamic fort, has sweeping 360-degree views across the park, with birds swooshing by above and below. It's signposted up a steep winding road off the EX208, 8km south of Villareal de San Carlos. The castle can also be reached via an attractive 8km, 1½-hour walk from Villareal, along the so-called Ruta Roja (Red Route).