to the end of the world?

The Camino follows an old road to Cabo Fisterra (= the Cape at the End of the World) which was previously used by the Celts. There the sun sets and both the underworld and the world of rebirth begin. In the Middle Ages many Christian pilgrims followed this old example, by walking on to Fisterra after Santiago.
Nowadays this old tradition is followed by more and more pilgrims. It has even led to a variant: a "detour" via the pilgrim’s town of Muxia to Fisterra. (There are also pilgrims who walk from Fisterra to Muxia, to end their journey there).
Extra distance:
> Santiago - Fisterra: 90 kilometers
> Santiago - Muxia - Fisterra: 112 kilometers

More and more guidebooks to the Camino Francés also describe the additional route to Fisterra and Muxia.

 Federación Amigos del Camino de Santiago: Prolongacion Jacobea
Confraternity of Saint James: Pilgrim Guides On-line > Finisterre Camino de Finisterre
Jakobus-info: Camino Finisterre/Muxia