Trail of el desfiladero de Pancorbo Activity · Pancorbo, Ebro, Burgos The Pancorbo gorge, known as the Gate of Castile, is a historic and strategic passage in the Montes Obarenes, where the Oroncillo river cuts its way between vertical walls towards the Ebro valley; it has been used since ancient times as a natural passage between the Basque Country and the Castilian plateau, and today the N-1 road, the AP-1 motorway and the Madrid-Irun railway line all cross through it. The walking route follows the ravine between these walls and climbs to the ruins of Santa Engracia, a fortress built in 1794 at the top of the gorge, next to the remains of the early medieval castle of Santa Marta; from the path there are views over the stepped hamlet of Pancorbo, with the motorway and railway line hemmed in the same cut. Photo: Javierme Javier Mediavilla Ezquibela (CC BY 3.0) What to see and do in Pancorbo