One of the most visited attractions in York is the Minster. Work started on this present building in 1220 by Archbishop Walter de Grey, after the previous Norman Minster was deemed unsuitable. Work continued for some 250 years and is the largest gothic cathederal in Northern Europe. The size and grandure of the building is quite remarkable. It has more Medieval stained glass than any other cathederal in Britain. The Great East window was built by John Thornton in 1405-8, it covers an area of 194 sq m and is the largest expanse of Medieval glass in the world!  Restoration work to the outer fabric is an on going project.