Maastricht's Church of Our Lady is one of the important survivors of the Mosan group of Romanesque architecture. Although its earliest predecessor was built in the 4th century, the oldest parts of the current church probably date from the late 9th century. Apart from several smaller additions in Gothic style, the church is still completely Romanesque.
Of special interest is the unique western facade which was built around the year 1000. It's a so-called westwork; a wide, almost completely closed tower flanked by stair-turrets, like many other churches in the Mosan region (the archdiocese of Luik/Liège) once must have had. Of this type of westwork, this is the only one that has survived intact, although its uppermost part of dates from the 13th century, and is built in a late-Romanesque style. A later type of westwork can be seen at the St. Servatius. Inside the westwork, which served both religious and defensive purposes, are several spaces, one of which is the choir for the parish. Attached to the church was a chapter of canons, which had a choir of its own in the eastern part of the church. After 1342 a new church was built for the parish next to this one, the St. Nicolaas, but nothing of that church remains since its demolition in 1837.
Behind the westwork is a basilican church from the 12th century, which looks far more conventional. However, the two pseudo-transepts the nave has on each of its sides are special. These were built to give extra strength to the structure so it could have stone vaults. The apse of the eastern choir is flanked by two towers with massive stone spires.
Several changes in a Gothic style have been made to the church, mostly in the form of new additions to the old church. The church's current main entrance is in a Gothic style and is located next to the western facade, giving the impression that it's a completely different building. Behind the entrance is a Gothic baptistry from the 15th century. In the 16th century the church was expanded with a Gothic archway which surrounds a courtyard.