In World War II, Mainz was a target of Allied bombing multiple times. The cathedral was hit several times in August 1942. Most of the roofs burned, and the top level of the cloister was destroyed. The vault, however, withstood the attacks and remained intact. The damaged elements were restored as authentically as possible, a process which continued well into the 1970s. In addition, much of the glass in the cathedral was replaced.The outside of the cathedral was colored red to match the historical buildings of Mainz. In addition, extensive cleaning and restoration efforts were undertaken, ending in 1975. In that year, the thousandth year since the beginning of the cathedral's construction was celebrated.In 2001, new efforts were begun to restore the cathedral both inside and outside. They are expected to take from ten to fifteen years.