Gorge of Pancorbo Nature · Pancorbo, Ebro, Burgos The Pancorbo gorge, in the Montes Obarenes (Burgos), is a natural and historic passage between the upper Ebro valley and the Bureba, the gateway to the Castilian plateau, for which it is known as the Gate of Castile. The Oroncillo river cuts its way through this rocky wall, forming a shadowy ravine with vertical walls through which human, animal and plant migrations have always passed between the north of the peninsula and the plateau. Because of its strategic value it has always been under military watch, as attested by the remains of fortifications in its surroundings, among them the castle of Santa Marta and the fortress of Santa Engracia, from 1794. It is included in the Montes Obarenes-San Zadornil nature park. Photo: Javierme Javier Mediavilla Ezquibela (CC BY 3.0) What to see and do in Pancorbo