Situated as it was, amidst what was termed the _Pré-aux-Clercs_, the resort of students and other bellicose persons, it became necessary to guard against assaults and incursions, by surrounding the monastic buildings with fortified walls and a moat, strong gates and watch-towers, from whence to keep an eye upon dangerous neighbours. Later, when students at the University had become more civilized, when danger of civil war had faded away, and the Huguenots had been suppressed, streets took the place of the moat, and houses occupied the site of the fortifications. At the commencement of the last century the monks built several large houses from plans by Victor d'Ailly, for artisans and labourers; but for the privileges obtained by living within the abbey precincts they paid a heavy rental. These habitations formed the Rues Childebert, Ste. Marthe, Cardinale, Abbatiale, and de Furstemberg--all within the walls. Originally there were two cloisters situated to the north of the church, but with the exception of a portion of the larger one, which has been converted into dwelling-rooms, they have been completely destroyed. The round arches and Doric pilasters belong to the 17th century; the older part, which was built by Abbot Eudes, was cut through and improved away, for the completion of the Rue de l'Abbaye. The same streets, and the houses thereof, have also to answer for the destruction of the refectory, the chapter-house, the great sacristy, and the Lady Chapel, to which the little cloister gave access. The refectory was a large hall constructed during the life of Abbot Simon by the celebrated architect of the Sainte-Chapelle, Pierre de Montereau. It was filled with stained glass bearing the arms of France and of Castille, some fragments of which may be seen in the church. The stone statue of Childebert, that stood at the entrance gorgeous with painting and gilding, is now in the Renaissance Museum of the Louvre. Dom Jacques Bouillart, describing the refectory as built between 1239-44, speaks of this statue as "apparently modelled upon a more ancient one."[87] De Montereau was also the artist-builder of the chapel of the Virgin, commenced under abbot Hugues d'Issy, who died in 1247, and finished under Thomas de Mauleon, who resigned his dignities in 1255. This chapel had but one rival, the _chef-d'œuvre_ of its architect; but all authorities speak of the beauty and gracefulness of the Lady Chapel, and its similarity to the Sainte-Chapelle in style and plan. When the great architect died, in 1266, the then abbot Gérard de Moret, desiring to perpetuate the memory of him who had done so much to beautify the convent, caused a magnificent tomb to be erected in the chapel of his creation. Pierre was represented with a rule and compass in his hand, and the epitaph describes him as _Flos plenus morum_ and _Doctor latomorum_.[88] Gérard be Moret was the builder of the chapter house, an oblong edifice divided into two naves by a row of four central