The joint creation of Lanfranco and Wiligelmo is a masterpiece of human genius in which a dialectical relationship between architecture and sculpture was achieved in Romanesque art. The Modena complex bears exceptional witness to the cultural traditions of the 12th century and is one of the best examples of an architectural complex where religious and civic values are combined in a medieval town.
Modena is located in the Po plain at the crossroads of the ancient Via Aemilia linking Piacenza with Rimini and the road leading to the Brenner Pass.
The construction of the cathedral, dedicated to San Geminiano, and of the bell tower was decided when the Bishop's See was vacant. The inscriptions in the cathedral and the text of the Relatio translationis sancti Geminianiprovide invaluable evidence of the first phase of building (1099-1106), and mention the names of the architect, Lanfranco, and the sculptor, Wiligelmo. The new cathedral had to be larger than its predecessor, built by the schismatic Bishop Eribert in 1070, to prove that the clergy and people of Modena had returned to the Roman Catholic Church. Construction of the cathedral and the bell tower took place in an urban structure already largely formed. The cathedral was built on the site of that built by Bishop Eribert and destroyed to make way for it, on an axis oblique to the original. The Maestri Campionesi, architects and sculptors commissioned to maintain the building by the cathedral's works office from the second half of the 12th century onwards, opened two side portals and the rose window in the facade, followed by the Porta Regia on the southern side (around 1180). Inside they enlarged the crypt, raised the choir, and expanded the roof in order to build a false transept (end of the 12th to start of the 13th centuries). The bell tower, whose tall silhouette is a landmark to travellers approaching the town, is closely linked to the cathedral by two arches.
Only minor changes have been made to the Piazza Grande. Its quadrangular shape has been preserved, and it has been lined on its northern side by the flank of the cathedral. The old and new Palazzi Comunali were connected by the clock tower (13th to 16th centuries) and blended in by the means of new facades and arcades (17th to 19th centuries). The brick Archbishop's Palace, closely connected to the cathedral by a private passage, is on the western side of the square. It underwent a first transformation at the end of the 15th century, and an additional floor was added in 1776. Further changes were made in ensuing decades. The appearance of the southern side radically changed when the new Law Courts were built by Luigi Giacomelli in 1892 (replaced by a new building by Gio Ponti in the 1960s). The bell tower (Ghirlandina) and the cathedral are indivisible in both physical and stylistic terms. This monumental tower, built from the same materials as the cathedral, consists of six floors emphasized by small blind arcades lit by simple openings, and then by two- and then three-light windows on the upper floors. The austerity and power of the bottom half of the tower, which is reminiscent of Roman structures, is surmounted by an octagonal drum and an upper lantern which express the new feeling of the Maestri Campionesi for Gothic architecture.
Lanfranco clad his new cathedral in Istrian stone, to give it the splendour of the temples of antiquity. The six portals along the wall feature Roman-style open lunettes and architraves. The all-brick interior has largely preserved its original structure, a nave on which opens an unfloored gallery and tall windows, two aisles, and a choir raised above a crypt ending in three straight apses. The arches are supported by a system of alternating marble columns with Corinthian capitals sculpted by Wiligelmo. The Maestri Campionesi introduced the false transept and the vaulting on the nave; they were undoubtedly also involved in the interior decorations when the decision was taken to paint the walls and decorate the architecture with facing painted to resemble brickwork, particularly on the main arches, the pilasters in the large bays and the friezes running along the walls. Modena Cathedral was also a large sculpture workshop, brilliantly illustrated by Wiligelmo, particularly in the facade, which is a veritable corpus of the sculptor's work.