SAN ADRIAN TUNNEL

To get to the San Adrian Tunnel, you will have to take the path from Zalduondo that leads to Zumaraudi. There, take the paved road known as the "mouth of hell" (la Boca del Infierno), which is deep and dark, and cross the 70-metre-long San Adrián natural tunnel (there is a small hermitage there), which leads to the province of Gipuzkoa. At the end of the tunnel, you will come across a stone arch, the only remnant of the old castle that once stood there. A crossing full of symbols!