Why St Paul’s Dome Has Three Layers
Stand on the Millennium Bridge and look towards St Paul’s. The dome is the easiest thing to pick out on the skyline. Step inside the cathedral and look up again. The curve you see from the floor belongs to a different part of the building.
Christopher Wren’s design uses three layers. The inner dome gives the cathedral its ceiling. A concealed brick cone carries the weight of the stone lantern. The outer dome gives London the profile you can see from across the Thames.
Why go to all that trouble? Wren could set the height and shape of the ceiling for people inside, while giving the dome a taller silhouette outside. The brick cone does the structural work in the space between them.
On a walk from the South Bank, try looking for the lantern first. It’s the stone structure at the very top of the dome. Once you know what holds it up, that familiar view becomes an engineering drawing you can read from the other side of the river.
Gordon Thom, London black cab driver and City of London Guide
London Taxi Tour (LondonTaxiTour.Com)








