Construction of the stone kremlin walled fortress, usually known as the Detinets, began in 1044; in the following year Prince Vladimir (reigned 1036-1052) replaced the wooden cathedral with a grandiose stone structure, the cathedral of St. Sophia. Although clearly modelled on the cathedral of St. Sophia at Kiev, Novgorod's cathedral is more austere in appearance, lacking decorative details. Its huge cruciform mass has a north-south orientation rather than east-west and is surmounted by a central dome on a tall, broad drum encircled by four smaller domes. In the south-west corner a domed tower houses a staircase. It is the cathedral church of the Archbishop of Novgorod.