The cathedral, which combines a Romanesque nave and a High Gothic choir, is notable for its rich collection of stained glass and the spectacular bifurcating flying buttresses at its eastern end.

Although there is no archaeological evidence for the building phases prior to 1080, the history of the bishopric and its cathedral is extensively detailed in the 9th century Actus pontificum Cenomannis in urbe degentium.

The 134-meter-long (440 ft) cathedral occupies the northeastern corner of the old town (known as Vieux Mans or the Cité Plantagenêt), an area on top of a slight ridge dominated by cobbled streets and half-timbered houses.

The current nave is of a typical Romanesque basilica form, with round-arched arcades and single aisles either side of a larger central vessel lit by clerestory windows.

Whereas the previous buildings had all featured a wooden roof, Bishop Guillaume's new nave, which today survives largely intact, incorporated stone vaults.

The capitals of the nave piers are richly carved, some with classical acanthus leaves, others with more naturalistic vegetation, and incorporating a range of animals and human figures.

[2][3] The Le Mans architect combined this Bourges-style design with a number of details borrowed from Chartres cathedral, most notably the elongated chapels radiating from the apse and the treatment of the external flying-buttresses as decorative elements as well as structural supports.

Stylistically and in its overall design, this portal is closely related to the Portail Royale at Chartres Cathedral and the west facade at the Abbey Church of St Denis, with which it is roughly contemporary.

The archivolts are carved with scenes from the Life of Christ, some of which are squeezed rather awkwardly into the cut-down voussoirs, suggesting they may have originally been intended for a different doorway, or else that the design was changed during construction.