The Upper Tajo river, on its course through Guadalajara, has created a landscape filled with gorges and ravines amid sierras and forests. Ocentejo, on the banks of the Tajo river, is one of the most interesting sceneries in this area. In Ocentejo we find "Hundido de Armallones", a rocky structure that formed in the 16th century, when the peak known as El Alar crumbled down. Around this area we can also visit the Inesperada Salt Mines, where we can admire the old warehouse, the troughs, and the channels that make up the salt factory. On top of a huge rock, we can still see the remains of an ancient castle of Celtiberian origin. The parish church of Ocentejo keeps some Baroque precious-metalwork pieces from the 18th century.