The accepted title for the district of the city which hosts the Fools' Guild's ownings in Quirm, housing the Guild's summer school, and local Quirmian branch, and a special retirement home for geriatric Clowns. The Collapsed Tower of Quirm is part of the site. Originally the independent Quirme Société Joyeux before being incorporated into the Ankh-Morpork Fools' Guild. La Sorbumme has something, er, fundamental, in common with Müning.
Sorbumme being a very close homonym for La Sorbonne, the name generally used for the University of Paris.