Camino del Interiór or Ruta del Túnel
Irún-Sto Domingo/Burgos
200km (approx)
Highest point: Túnel de San Adrian 1150m
In the course of the Middle Ages, the old Roman road Pyrenean crossing at Roncesvalles was replaced by the coastal crossing at Irún. Burgos and central Spain were reached via this route, which remains the main road today and was later used by the railway.
The pilgrim route, from Irún to the Camino Francés via Tolosa and Vitoria, uses a shortcut through the mountains via the natural tunnel of St Adrian. At La Puebla de Arganzon the route forks, one branch going to Santo Domingo de la Calzada, the other to Burgos.
See overview on Eric Walker's site. The Basque Country tourist board site has a full description to the route in its area, and the Guipuzcoa Amigos have a detailed description on their website. There is also some information on the route in Álava, sometimes known as the Ruta Alavesa, on the Álava Amigos site. The CSJ and Guipuzcoa guides describe the Santo Domingo branch. There is an overview of the Burgos branch, aka the Ruta Mirandesa, on Turismo Burgos site, and one on the Sto Domingo branch on the La Rioja Amigos site.
Confraternity of St James produces English: guide | factsheet