The main part of the romanesque monastery is a long 11th century building on the north side, along the nave of the church. It is built on three levels: the first two are stone vaulted, the third one is pannelled.
To the north of this building, annexes from which a part is gone contained an infirmary at the Dormitory level and a kitchen at the Promenoir level.

Outline of the Romanesque Abbey
At the forefront in white, the first buildings
The Dormitory, who has lost two thirds of its length when the front collapsed together with the three last bays in 1776 , is today used as the second Library.

The monks’ Promenoir, which was the Refectory and the Chapter hall.

The Aquilon crypt which was the Almonry.

 Visit the Promenoir of Monks
Visit the Aquilon Crypt
Section of the main building
During the 12th century, construction keeps going especially on a large complex on the north flank of the rock. We know almost nothing of these buildings which occupied the actual site of the Merveille; we know however that they had two storeys, each separated by two rooms, the bottom one covered with vaults, the one above pannelled.

To the west, a part of the occidental porch has been walled in and converted in two small rooms. Above were Robert de Torigny apartments, down on the lower level a room which was possibly used as a guards room. Lower still, at the very bottom of the basement, are two dungeons called “the twins”; their only access is a trap-door in the ceiling.
Finally, to the south-west, the abbey, Robert de Torigny established a series of buildings between the Ossuary and the western terrace. The main one was a large building including, above a storey of deep caves, a large hall covered with pointed barrel vault, usually called the Hostelry, over which there is a floor under a framework of which purpose we know nothing. This building collapsed in 1818, but the 18th century scale model shows us the illustration. Between the Hostelry and the Ossuary there was a small construction made up of two levels: the level below was a vaulted room and the one above was chapel Saint-Etienne. We also know nothing of this building.

west view
In color, the romanesque Monastery
south view
In color, the romanesque Monastery - At the forefront, the Hostelry.
Thus, the romanesque Abbey was offering an impressive sight of a large and tall church at the summit of the Mont, surrounded by a belt of protective and solid buildings.