Peña Carrias Nature · Jurisdicción de San Zadornil, Las Merindades, Burgos Peña Carrias is a karst massif that rises to 1,130 metres on the boundary between Valdegovía, in Álava, and the Jurisdicción de San Zadornil, in Burgos, between two natural parks: Valderejo, on the Basque side, and Montes Obarenes-San Zadornil, on the Castilian side, with dense forests of beech, oak and pine. It is a long, narrow limestone wall, a remnant of the old cover of the Lahoz anticline, forming ridges more than a kilometre long and up to two hundred metres of vertical drop, whose jagged crest makes reaching the summit very dangerous; its verticality gives it a distinctive look and a demanding climb, with routes from Bóveda, Tobillas and, above all, from Arroyo de San Zadornil. In 2014 Peña Carrias was fixed as the sole official place name, ruling out a Basque origin. Photo: Mikel Arrazola (CC BY 3.0 es) What to see and do in Jurisdicción de San Zadornil