Dating to the late 12th century St. Kentigern's Church is a good example of the transitional period of architecture, half way between the Norman and Gothic styles. The inside of each window in the south aisle is Norman and the outside is Gothic. The south doorway is a fine example of the early Gothic.
An earlier church may have been on the site. Evidence of this is its position far outside the medieval core of Lanark and to a piece of stone with an interlaced design found used as blocking in one of the lancet windows in the south aisle.