" The Dome"

The dome exerts thrusts around its circumference.

This thrust has to be counterbalanced if the structure is to be stable and resist collapse.

An example of where this occurs is the Pantheon in Rome where the dome which spans 43.3m is supported by eight huge piers.

Another famous example of domed construction can be seen in the picture above of the Santa Sophia church in Istanbul. The span of the central dome is 30m and the main dome is further supported by semi-domes. The reult is a floor length of 69m that is unbroken by columns.