William the Conqueror died at age 59 after he fell off his horse. He died in the Convent of St Gervais in Rouen. He got burried in the Abbaye-aux-Hommes.
The story is that on the day of his burial, it was so hot that the body in the stone coffin started to "explode", and the church had to be evacuated.
In 1562, looters tole his body and the content of his tomb. The monument, built 80 years later is supposed to contain only a thighbone of William.