The San Marcos River Nature · Arroba de los Montes, Montes de Ciudad Real, Ciudad Real Image of Arroba de los Montes, not of the place itself. The San Marcos river rises in the natural district of the Montes de Toledo, in Ciudad Real, and is a tributary of the Guadiana. It runs through and drains the municipalities of Fontanarejo and Arroba de los Montes; just a few metres before it flows into the Guadiana it joins the Valdehornos river, downstream of the Hoces gorge and the Tabla de la Murciana. It is a seasonal watercourse, with a rainfall-driven regime showing torrential traits, winding and cut into quartzite and slate materials; in the past it powered several flour mills, one of which is preserved in Fontanarejo. Along its channel, narrow and deep, restoration works with gabions have been carried out to slow the supply of stony material. Its banks and the surrounding sierras are home to deer, wild boar and a notable community of birds of prey. Photo: 19Tarrestnom65 (CC BY-SA 4.0) What to see and do in Arroba de los Montes