The Kadagua River will be left behind as we climb the high pastures that close the municipality of Zalla to the south. It won’t take long for us to feel the fresh air from the heights blowing over the hills as we contemplate the neighboring lands of Aiara.

130m | 0km

We parked at La Herrera Cemetery, near the Landabaso neighborhood. We take the concrete track which branches off when crossing a Canadian pass. We continue to the right between the Atlantic countryside and small patches of native forest.

10 minutes | 190m | 0.7km

The track zigzags up the hill and branches off around a curve. The left branch goes up to a farm. We go right. The peaks of La Garbea, El Balcón de Las Encartaciones, Ubieta, Alen and Kolitza stand out over the Kadagua Valley.

47 minutes | 285m | 3.5km

The route makes a wide detour under the eastern slope of El Mazuco before the next fork. To the right we come to a concrete track which, almost immediately, unfolds. We go to the left, a wide gravel track. We leave the repopulation of conifers and observe the grassy hills of Espaldaseca, at the top. We go to them.

52 minutes | 325m | 3.9km

There is a new piece of countryside and we pass next to a field planted with fruit trees, the Arbolar de Cano. At the end of the fence, we leave the comfortable gravel track that goes towards the district of Zokita. We climb between reforestation to a wide dirt road that continues up the mountain.

1h 5min | 470m | 4.6km

You come out on a wide gravel track which branches off immediately. We go to the left. At the edge of the road a traffic light prohibits the circulation of unauthorized vehicles.

1h15 | 580m | 5.3km

We reach the upper ridge of the sierra, the wide pass that opens between the summit of Celadilla, on the right, and Espaldaseca, on the left. To the north is the encartado valley of Kadagua, in Biscayan territory, and to the south, the luminous valley of Aiara (Ayala), framed by the long escarpment of the Sierra Gorobel (Sálvada). A cross of signs, overflowing with arrows and signs, guides us to the top.

1h25 | 696m | 5.7km

We climb to the left and, through wide meadows, we reach the top of Espaldaseca. The views are spectacular: from the Cantabrian Sea to the mountains of Lunada and the main mountains of Vizcaya.

For the descent we headed for the clear slope that plunges to the north. We find a track next to which stands a slender and curious mugarri, an eye carved in stone, from which we descend the track to the left. We stand at a fork next to the beacon we pointed out earlier. We take the track that descends to the right and begin a long flank on the northern slope of the mountain range towards La Brena and Bolunburu.

2 hours 10 minutes

We cross a wide track that comes from the district of Zokita, and we continue to descend.

2 hours 25 minutes | 370m | 9.9km

The track veers sharply to the right. We leave it by a path that advances along the edge of the ridge in the shade of the repopulation of conifers, heading north. Going down we come to a forest track along which we descend to the left to the ravine of La Brena.

1h35 | 285m | 10.7km

We cross the stream and on the other side we find the marks of a local GR and a PR. At a fork, we leave the path that will take us back to the valley later. We go up the branch on the left towards the nearby Iron Age fort.

1h45 | 315m | 11.3 km

The Bolunburu fence was discovered in 1998. The defensive ring that shapes the castro is formed by a wall which in its original state was four meters high in some places. Some panels tell us about the discoveries made in this Iron Age site. From the top, to the north, we govern the Kadagua River Basin.

We retrace our steps to the ravine and follow the track down the mountain, keeping close to the stream that descends in small jumps through jungle-like terrain.

2 hours 20 minutes | 124m | 13.4 km

We cross a pass under the dual carriageway of Kadagua and continue until it meets the bidegorri that comes from Zalla. We cross the river by a wooden footbridge which gives access to the Bolunburu recreation area.

We continue along the river along the Camino de Santiago and pass the remains of the old forge and mills of Bolunburu, the hermitage of Santa Ana and the majestic tower. We follow the road through the river valley, walking parallel to the canal which carries its waters to a small power station.

3h55 | 109m | 16km

We cross a tunnel under the railway and come out on the road which, on the left, goes towards Balmaseda. Along the shoulder, between old dilapidated feverish installations, we travel the three hundred meters that separate us from La Herrera.