This article accompanies the fable
The scallop shell is the traditional symbol for Christian pilgrimages. It is associated mostly with the pilgrimage to Santiago de Compostela in Galicia (the other two main pilgrimage sites being Jerusalem and Rome). The shell can be seen as small badges worn on clothing or on signposts or on buildings along the way. The traditional one is on the left; the modern one on the right. Photos: (L) Merlin; (R) Skarabeusz.
Why a scallop shell? Although there have been mythological explanations, the most likely seems to be that scallops once were found on the coast here and they became scooping tools for pilgrims. A useful site: http://www.santiago-compostela.net/
Also see Botticelli's famous painting The Birth of Venus on the lower half of this page: http://www.sexualfables.com/Titians-Venus-of-Urbino.php
In terms of what the pilgrimage route looks like today, a couple of representative images are below. The second image shows pilgrims on the bridge over the Órbigo River.
Photos - upper: Oula Lehtinen; lower: Green Cardamom.