There is a widespread assumption that the dome, or cupola, as it presently stands, was designed by Michelangelo, who became chief architect in 1546. In fact, Michelangelo's design called for a spherical dome. At the time of his death (1564), only the drum, the base on which a dome rests, had been completed. The dome proper was redesigned and vaulted, between 1585 and 1590, by the architect Giacomo della Porta, with the assistance of Domenico Fontana, who was probably the best engineer of the day. Fontana built the lantern the following year, and the ball was placed in 1593.