In the early middle-ages Maastricht was very important in the spreading of Christianity in the Netherlands. In the 4th century, the bishop St. Servaas was the first bishop in the Netherlands, and the Onze Lieve Vrouwekerk (which also is the oldest still standing building in the Netherlands) could be described as the root of Christianity in the Netherlands. Servaas' remains are still kept in Maastricht in a tomb.