Saint-Jean Abbey

This urban Benedictine abbey, founded by Saint Salaberge in the 7th century AD, occupied a large part of the city. It was ruined by the Hundred Years' War and almost entirely destroyed under Henry IV.
All that remains is the former abbot's residence, part of the 17th-century convent buildings and the 18th-century cloister with a superb staircase built around 1750. 
In the garden, a 15th-century church gate of unknown origin leans against the rampart. The granary located along Rue de Signier, which housed the departmental archives, was destroyed during the bombings of 1944. 

It should be noted that the abbey buildings are now occupied by the Hôtel de la Préfecture de l'Aisne, and are therefore only visible from the outside...