The Bidasoa is a river in the Basque Country of northern Spain (Basque Community) and southern France in the Pyrenees that runs largely south to north. Named as such downstream of the village of Oronoz-Mugairi (municipality of Baztan) in the community of Navarre, the river actually results from the merger of several streams near the village Erratzu, with the stream Baztan that rises at the north-eastern side of the mount Autza (1,306 m) being considered the source of the Bidasoa. It joins the Cantabrian Sea (Bay of Biscay, Atlantic ocean) between the towns of Hendaye and Hondarribia.
Cinco Villas de la Montaña or simply Cinco Villas (in Basque, Bortziriak or Bortzerriak) is a region and a sub-zone located on both sides of the Bidasoa River, in the north of Navarre.
It’s main tributary is the Baztan river.
The Bidasoa flows through much of its 66 km (41 mi) length over Navarrese territory, except for the last 10 km (6.2 mi), where it establishes the borderline between France and Spain, as well as the boundary between the Basque provinces of Gipuzkoa and Labourd. In line with the distribution of the river’s length, the bulk of its watershed’s area lies on Navarre (684 km2 or 264 sq mi). The basin holds 105 permanent streams and rivers that number 497 km (309 mi), the region being drenched in rains regularly. The Navarrese side of the basin (rural landscape) is inhabited by 22,000 inhabitants. 70% of its population have the sewage treated before spilling to the river.
But for the first 15-odd kilometres, the river clings to the north to south disposition of other neighbouring rivers of Gipuzkoa joining the Bay of Biscay, e.g. Urumea, Oria, etc. Strengthened by the waters harvested from the sides of the pass of Belate, downstream of Doneztebe the river heads north and crosses the town of Bera at the north end of Navarre before entering Gipuzkoa at Endarlatsa. From the town of Doneztebe on, the main road N-121 runs along till the roundabout across the river from the toll of Biriatu by the AP-8 (motorway). Next comes the quarter Behobia and the major towns on the shores of the estuary.
See here Andorra travel guide
See here Pyrenees travel guide
See here France travel guide
See here Spain travel guide