Located north east of the province of Guadalajara is the Hayedo de Tejera Negra Nature Reserve. The rivers Lillas and Zarzas have eroded deep valleys that run parallel to each other and edge the outer limits of the reserve. The reserve is home to vegetation that would normally been seen closer to the Atlantic. The height of the Sierra has helped to create a microclimate which has enabled beech groves to survive. This is the most southern beech grove in Europe. The reserve covers a total of 1391 Hectares.
Visits must be arranged through the Visitor Centre, located one kilometre outside of the town of Cantalojas.
The Hayedo de Tejera Negra Nature Reserve is home to an important amount of birds of prey. These include golden eagle, red kite and goshawk. Mammals include roe deer, the fox, wild cat, marten, badger, weasel, wild boar.
Apart from the beech trees there are yew, holly, birch, oak, hazel and pine.