The Tunnel Way is also known as the Tunnel Route, the Basque Inland Route and the San Adrian Route. In the Early Middle Ages, when the Northern (Coastal) Way was subject to the Vikings' skirmishes and Muslim presence and forays threatened pilgrims and trade routes in the borderlands, the Tunnel Way provided a safe road north of the frontier area, i.e. Gipuzkoa and Alava. This may be the oldest and most important stretch of the Way of St. James up to its heyday in the 13th century. From the starting point in Irún, the road heads south-west up the Oria valley (Villabona, Ordizia, Zegama), reaches its highest point at the San Adrian tunnel and runs through the Alavan plains (Zalduondo, Salvatierra/Agurain, Vitoria-Gasteiz and Miranda de Ebro). Yet previous to the latter, nowadays pilgrims usually take a detour south towards Haro and on to Santo Domingo de la Calzada on account of its better provision.