 It is not uncommon, for example, for a part of building that has been constructed over a lengthy period extending into the 12th century, to have very similar arcading of both semi-circular and pointed shape, or windows that are identical in height and width, but in which the later ones are pointed.This can be seen on the towers of Tournai Cathedral and on the western towers and facade at Ely Cathedral.Other variations that appear to hover between Romanesque and Gothic occur, such as the facade designed by Abbot Suger at the Abbey of Saint-Denis, which retains much that is Romanesque in its appearance, and the Facade of Laon Cathedral, which, despite its Gothic form, has round arches.