The climatic diversity produces a range of vegetation and ecosystems, and trees such as oaks, juniper, pine, beech, etc. can all be found in the province. The seasonal distribution of rainfall is influenced by the relief, the most rainfall occurring in the mountainous areas of the Sistema Ibérico with between 700 and 900 mm per year, and in the headwaters of the Jarama and Sorbe rivers in the Sierra de Ayllon, with more than 800 mm. The Henares and Tajuña valleys, and the northern area of moorland in Sigüenza have less than 600 mm annually on average, and in some areas such as the Molina moorlands, bordering the provinces of Zaragoza and Teruel, rainfall may be below 400 mm. The province contains the comarcas of La Alcarria, La Campiña, La Serranía and Señorío de Molina-Alto Tajo. Landmarks of note include the castle and walls of Palazuelos, Palace of El Infantado, Ducal Palace of Pastrana, Palace of the Dukes of Medinaceli (Cogolludo), Sigüenza Cathedral, Cueva de los Casares in La Riba de Saelices and Castillo de Pioz. The Co-cathedral of Santa María de la Fuente la Mayor in the city of Guadalajara was declared a "Bien de Interés Cultural" site in 1941. Standing high on a rock, Atienza Castle can be seen from miles around. It frequently changed hands between the Moors and the Christians until it was finally retaken by Alfonso VI in 1085. With foundations dating back to the 5th century, Sigüenza Castle was extended by the Moors and retaken for the Christians by Bernard of Agen in 1123. In the late 18th century, Bishop Juan Díaz de la Guerra changed the appearance of the fortress into that of an episcopal palace but during the War of Spanish Independence it was taken by the French who seriously damaged it. In the 1830s, it was devastated by fire and had to be abandoned. After being fully restored, the castle was opened as a parador luxury hotel in 1976. Decorated with banners and suits of armour, the huge lounge is the castle's original dining room. The Castle of Molina de Aragón is located on a hill commanding the surrounding valley, and is formed by an external line of walls with four gates and six towers of which four are currently in good condition.