The Ubierna valley Nature · Merindad de Río Ubierna, Burgos (Alfoz), Burgos Image of Merindad de Río Ubierna, not of the place itself. The río Ubierna comes down from the páramos of the north towards the Arlanzón set between slopes of holm oak and gall oak, with a floor of narrow flood plain where the villages and the poplar groves of the merindad line up. Photo: Thomas Holbach (CC BY-SA 4.0) What to see and do in Merindad de Río Ubierna