It took until 1345 before the cathedral was completed, partly because the design was enlarged during construction. The result is an overwhelming building, 128m long (420 ft) with two 69 meter tall towers (226 ft). The spire, which reaches 90m (295 ft), was added in the 19th century by Viollet-le-Duc. The Notre-Dame Cathedral has several large rose windows, the northern 13th century window is the most impressive. The massive window has a diameter of 13.1 meter.