‘so, why is Grasse there?’

Grasse sits high above the valley below, with the twin towers of the cathedral and the old Bishops' Palace on a small knoll, the Puy, close to the edge of its ancient site.

Historic settlements virtually everywhere were based on three factors: security, the availability of water and ample food sources.  Grasse’s site vividly demonstrates all three.  The hinterland, with hills to the north offering pasture and the fertile flat land below providing arable land, was suitable.  Water pours out of the springs above the town, especially Le Foux and the Riou Blanquet.  And above all, the key is the geomorphological accident of the promontory half way between the flat plain of the now Plan de Grasse and the intermediate peaks of the Roquevignon and the Plateau Napoleon.  At 200 metres above the valley floor where the railway station now stands and protected to the north by steep hills, it’s a spacious natural fortress. 

Just try taking the various ‘traverses’ from the station up towards the old town or else the steep descent to the town on the route Napoleon, imagine where the walls were and you’ll see why. The original settlement, where the cathedral and the old bishops' palace now stand, was on the small knoll slightly elevated above what is now the town, so it’s not surprising that the official name of the cathedral is Notre-Dame-du-Puy (‘Our Lady of the Height’ or maybe even ‘Our Lady of the Balustrade’ - you can see the derivation here). The original town walls surrounded only the Puy: they were much extended in the later twelfth century to allow the growth of the settlement to the north of the Puy. If you visit the Maison du Patrimoine, you can see three maquettes which vividly show how Grasse developed: a photo doesn't do them justice, but here is one of them:

For the original inhabitants, the site was safe, relatively flat and had plenty of reliable water streaming from the steep hills behind.   And what made it thrive and become a significant town, rather than just a secure village like Bar sur Loup or Gourdon?

For a start, the promontory was relatively spacious – 400m by 400m, quite large enough for a medieval town.  A few vestiges of the walls, which followed the terrain quite closely, remain.

Approximate area of old town, with the Riou Blanquet to the north and east.

And then the site was ideal for two medieval industries, namely tanning and milling.  Water tapped from the Foux was routed by multiple small channels on to the Puy and supported numerous tanners in the town, using the ample supply of goatskins from the surrounding hills.  And immediately to the north and east, there’s the precipitous valley of the Riou Blanquet, ideally suited for the construction of mills of all kinds. This 'Quartier des Moulins' is best seen today from what was once the railway bridge of the Chemin du Sud:

Finally, look at a larger map:

Grasse is only 15km from the sea, over mostly flat land once you’re at the bottom of the Puy.  Movement by sea was by far the fastest method of travel in medieval times, and Grasse, from its location on the edge of the hills, secure against pirates from the sea, could communicate and trade with Mediterranean towns.  With Genoa, one of the most powerful city states in Europe in the twelfth and thirteenth centuries, in particular, Grasse had a thriving trade relationship.

A powerful combination of circumstances!