Here is an interior view of Exeter Cathedral, showing the massive columns which allow the roof to be the longest unsupported roof in Europe. When the Cathedral was being built, with the usual single tower, the builders had news of another newly-built Cathedral, whose central tower had collapsed. So they built two towers in this Cathedral, to spread the load. On 4th May, 1942, Hitler ordered the destruction of Exeter by bombing, in retaliation for the British bombing of Berlin. The Cathedral was only saved by the strenuous work of the fire-wardens, who stayed on the roof all night long, coping with the hundreds of incendiary bombs which landed on the Cathedral. As it was, the Cathedral lost 500 tons of stone from its structure that night, but survived the onslaught.