 The minster was formerly the collegiate church of Essen Abbey, founded in about 845 by Altfrid, Bishop of Hildesheim, around which the city of Essen grew up.The present building, which was reconstructed after its destruction in World War II, is a Gothic hall church, built after 1275 in light-coloured sandstone.The octagonal westwork and the crypt are survivors of the Ottonian pre-Romanesque building that once stood here.