A map of Morbihan (the Departement)

To right of centre there's a rectangle a couple of
shades brighter than the rest.
That's the area round La Tronconnais, including
Malestroit.

Most of the places mentioned on this site are on
this map, which I've repeated, with the
appropriate highlight, on their various pages.
Here's a blowup of the highlighted area:
The Dot Marks the Spot