THE SMALL, CHARMING hotel near the village of El Bosque, at the entrance to the Grazalema Natural Park has magnificent views from all rooms. Beside the hotel, the Majaceite River is the most southern trout fishing area of Europe. This area is ideal for outdoor sports, hang glinding and excursions into the mountains. The town holds a National Award for Visual Improvement. El Bosque was founded by the Duke of Arcos, whose Palace of Marchenilla used to be here. It is scenically located on the edge of the Albarracin mountains. The town holds a National Award for Visual Improvement     HISTORICAL BUILDINGS   Church of Nuestra Senora de Guadalupe   El Molino del duque.   Ruins of Tavizna Castle, about 5 km from town. FESTIVALS   St. Anthony, in June.   Evening Festival of St. John.   Summer Festival, in August.