of Sweden in the early 11th century. King Olaf II of Norway, known as St Olav, did much to enforce Christianity on the Vikings, and by the end of the 11th century, Christianity was the only legal religion. In Denmark, Christianity was promoted by Canute the Holy in the late 11th century, with Sweyn II of Denmark dividing the country into eight dioceses, and establishing many churches, cathedrals and monasteries from about 1060 onwards. Much of Sweden was united under Olaf Eiríksson around 995, with the southern area, Götaland being united with Svealand by Sverker I of Sweden in the 1130s. Lund Cathedral, Sweden, was made the seat of the archbishop for all of Scandinavia in 1103, but only the crypt remains from the 1130s, the rest being mostly 19th century rebuilding. Bishop Absalon founded Roskilde Cathedral in Denmark in 1158 and the city of Copenhagen (1160–67). Architectural influences came with clergy brought from England (such as Nicholas Breakspeare), Lombardy and Germany. The influence of English Norman architecture is seen particularly in Norway at Nidaros Cathedral, Trondheim, and of German Romanesque at Lund Cathedral, Sweden. Benedictine monks from Italy introduced the skill of firing bricks to Denmark. While most churches were initially built of timber, the larger ones were replaced by stone, with brick being the dominant material in much of Denmark where building stone is scarce. Small Romanesque churches are plentiful and are generally in relatively unchanged condition. Large churches are rare and are much altered as at Aarhus Cathedral, Lund Cathedral and Roskilde Cathedral. Norway has 25 wooden stave churches from this period, making up all but three of the world's medieval wooden churches. In Sweden, surviving Romanesque churches are concentrated mainly but not exclusively to three provinces: Gotland, Scania and Västra Götaland Characteristics The wooden stave churches of Norway represent a type that was once common across Northern Europe, but elsewhere have been destroyed or replaced. They have timber frames, walls of planks, and shingled roofs which are steeply pitched and overhanging to protect the joints of the building from the weather. Denmark has seven rotunda churches, which have a circular nave, divided into several storeys internally, and have projecting chancel and apse as at Bjernede Church and Nylars Church. At Østerlars Church, the chancel and apse are constructed as small intersecting circles. Rotunda churches also occur in Sweden as at Hagby Church. Bulky west towers with