 At Rouen Cathedral, two twelfth century towers flank a high tower in the Norman style tower capped by a very ornate flamboyant Gothic spire.Openwork spires of stone, sometimes of great height, were popular in the Flamboyant style, occurring singly at Strasbourg Cathedral, Burgos Cathedral, Freiburg Minster, Vienna Cathedral; and also at Cologne Cathedral and Ulm Minster, both designed in the mediaeval period but not realised until the late 19th century.In England, during the Gothic era, there was a continuing fashion for three towers, with the largest being that over the crossing.