The abbey is made up of a number of buildings constructed on Mt. Pirchiriano, situated at the beginning of the Val di Susa. According to some historians, in Roman times a military fort controlling the movement of traffic into Gaul already existed where the abbey is today; subsequently the Longobards built a fort as a bulwark against successive Frankish invasions. Today the abbey presents the visitor with an imposing fortress surrounded by a circle of defensive walls, designed both as a refuge for pilgrims as well as a deterrant to the brigands who once roamed the area.
The present complex was started in 999 A.D. and completed in only 36 years thanks to the magnanimity and faith of Ugo of Montboisser, a rich Lord from the French region of Alverne and to whom had been entrusted the task of building a great abbey as penance for his sins. According to legend, the Archangel Michael himself indicated and consecrated the place where the hermitage was to be built, and hence the edifice is named after him. An aura of mystery continues however to attach itself to this grandiose monument: the doorpost of the Door of the Zodiac, on which the stories of Cain, Abel and Samson are represented, is covered by a pagan representaion of the stars of the zodiac. This is a unique feature and represents the most ancient romanesque cycle of the zodiac and other constellations in existence.
The abbey has known both moments of splendour and decay: it was a place of pilgrimage, prayer and meditation for the medieval faithful, who having managed to cross the Alps, entered the Val di Susa before directing themselves towards Rome or the Holy Land, but it has also served as a military fort and a place of refuge, surviving both bombardments and earthquakes.
The main church has three naves and its structure shows the progressive movement from romanesque to gothic art. The paintings of the four major prophets, Isaiah, Ezechiel, Daniel and Jeremiah, situated to the side of the huge abbey window possess a suggestive beauty. The fifteenth century fresco which represent three scenes from the Virgins life, that of the burial of Jesus, the dormition (a rare subject in western art), and the assumption into heaven are also of great value.
The library is open to academics, students or the merely curious, it contains over eight thousand volumes, most of them dating from the nineteenth century, on topics as wide-ranging as the history of art, local history, theology e philosophy. The abbey moreover offers, by vocation and tradition, a dignified hospitality to those visitors who wish to make a spiritual retreat.