The Montes Obarenes-San Zadornil Natural Park Nature · Oña, La Bureba, Burgos Image of Oña, not of the place itself. The eastern sierra of the municipal district of Oña forms part of the Montes Obarenes-San Zadornil natural park, declared in 2006 in the northeast of the province of Burgos, on the boundary with Álava. The Montes Obarenes form the southernmost foothills of the Cantabrian mountain range and rise like a natural wall above the flat lands of La Bureba, with a Jurassic-type structural relief whose highest point is the Humión peak, at 1437 metres; the park, bounded to the north by the river Ebro, encompasses the sierras of Oña, La Llana, Pancorbo and Árcena. At this botanical crossroads, Atlantic beech and oak woods coexist with Mediterranean holm-oak groves, quejigo-oak groves and juniper stands, and on its cliffs red-billed choughs and cliff-dwelling birds of prey nest. Photo: WikiBurgos (CC BY 3.0) What to see and do in Oña