A team from the Institut National de recherches archéologiques préventives (Inrap) is at present working in the historic centre of Guerande, an opportunity provided by work on the squares as well as the parvis of the Collegiate Church of Saint-Aubin.

This important excavation, financed by the town of Guerande, gives us a unique opportunity of finding the answers to three questions first asked in the 19th century.

The mediaeval city of Guerande has it an antique origin? Recently discovered architectural elements (tiles, petit appareil stonework), in situ or destroyed, could well confirm this. Gallo-Roman pottery has been found during the excavation, but not in securely stratified levels.

The collegiate church dates mainly from the 15th century, but what about the two, or even three, earlier buildings on the site? Even though their precise age remains to be confirmed, the most ancient could date from Antiquity (1st-5th century AD), and the most recent could be Romanesque (11th- 12th century). In the 15th century the Gothic church was founded on these older buildings.

Froissart, the mediaeval chronicler, reports that in 1342, during the war of succession of Brittany, Guerande "was probably taken and looted". This account has been the subject of discussion since the 19th century. The Place de la Psalette discoveries seem to confirm an important break in continuity of occupation during the 14th century, when several houses were destroyed and a square was created in front of the collegiate church.