Then, in 1418, a competition
to renew work on the dome was announced by the overseers of the works.
The base for the dome was already in place and its octagonal shape determined
the size and silhouette of the dome, which had to span 138 feet, nearly
the 140-foot dimension of the great Roman dome of the Pantheon . Complicating
the design and the problem of construction was the height of the Florence
dome, which was projected to be 275 feet and was later increased to 285
feet.