Poza de Sal is about two kilometers from the old railway and we visit in the last stage that is less distance, it is worth the detour. Shortly after is Salas de Bureba, with an interesting group of ancestral houses and popular architecture. And also a couple of restaurants to recharge your batteries. The route of the Natural Trail passes through Castellanos de Bureba, Terminón and reaches the Oña station, rebuilt with good taste and equipped with recreational areas and parking lots. The historic center of Oña has been declared a Site of Cultural Interest and a detour is mandatory to explore its small streets with a medieval atmosphere full of stately houses and emblazoned facades, contemplate the imposing building of the Monastery of San Salvador and the portico of the church of San Juan, In the town hall square. On one side is the Sports bar, if you want to have a drink. The section between Oña and Trespaderme has been cut off until recently due to the works on the Oca and Ebro bridges, now it is perfectly conditioned and is a natural fantasy. The Buitre and Pastorcillo tunnels cross the Oca gorge and the greenway enters the La Sante jungle, an old palace with a romantic atmosphere that seems condemned to ruin and abandonment in a place with a certain mystery. Passing through the Horadada tunnel prevents us from contemplating the confluence of the Oca in the Ebro river and along a fantastic forest walk the Ebro bridge appears, recovered after some time in works to give continuity to the Santander-Mediterranean Nature Trail in Las Merindades, Burgos. .
The route passes through another tunnel and leaves the Horadada gorge, in the background is Trespaderne, which is the end of the next day. Now the trip continues along the gravel road to go up the Nela River basin to the foot of the Cantabrian Mountains, passing through the town of Nofuentes and then the old stations of Pradolamata, Moneo, Bustillo and Medina de Pomar appear, the town most populated in Las Merindades with 18 districts and 17 neighborhoods. Medina de Pomar has held the title of city since 1894, it is outside the greenway a couple of kilometers. The Velasco Castle, also called Alcázar de los Condestables, or simply Las Torres, is the building that attracts attention from the Nature Trail. In the historic center there are houses with emblazoned facades, palaces, stone streets, squares with arcades and original doors from the old medieval wall, a good reason to visit the town and learn about the historical and monumental heritage of the region. The railway route continues through the Nela valley, passes through several bridges rebuilt in the last refurbishment of the track and reaches the Villacaryo-Horna station, where we mark the end of the first stage. Access to the center and the picturesque Plaza Mayor is easy via Avelino Alonso de Porres Castro Street. Villarcayo is the capital of Las Merindades Burgos, it has all kinds of services.