The main dome is part of a more imaginative design of the drum than supportive. Its phenomenal shape could be obtained, using only wood and lead, but these materials were not sufficiently robust to be able to bear at the top of the stone lantern. What's more, each facing the dome seemed to be disproportionately high in relation to the entire cathedral. To resolve these problems, the aforementioned architect Wren has created a structure trójpowłokową. So you can see from the center of an internal ceiling dome, which is significantly płytszy from the outside. Outer dome was built only based on the attic above the drum, which further increases the whole structure. The last stone to the building itself has Wren and his son, after whose death was buried in the crypt of St. cathedral. Paul.