Book Five of the Codex Calixtinus, compiled around 1140 and generally attributed to Aymeric Picaud, is the oldest surviving guidebook to this road and reads remarkably like a modern one. It divides the journey into stages, lists the rivers and says which are safe to drink from, names the shrines worth a detour, warns about ferrymen who overload their boats and about toll collectors on the Navarrese passes, and delivers opinionated verdicts on the character of the peoples along the way, most of them unflattering. It also describes the cathedral at Santiago in detail, which makes it a source for the building as well as for the road.
The Camino Frances is not simply a path across an existing landscape. It made much of the landscape it crosses. The Navarrese and Castilian kings of the eleventh and twelfth centuries actively developed the route, granting charters to new towns along it, inviting French settlers, the francos, to populate them with trading privileges, and building bridges: Puente la Reina takes its name from the queen who paid for its bridge. Streets in Pamplona, Estella and Burgos still carry the name of the road.
The religious infrastructure followed. Cluniac and later Cistercian houses, the Romanesque churches of Fromista and Eunate, the pilgrim hospitals, and the military orders, notably the Order of Santiago, whose stated purpose included protecting pilgrims on the road.
The meseta, the high plateau between Burgos and Leon, is the section walkers argue about most. It is flat, treeless and hot, many skip it by bus, and a substantial body of pilgrim writing insists it is the part that does the work.