When Michelangelo died in 1564, the walls were being built, the piers had been strengthened and everything was ready for the building of the dome. The Pope wanted Michelangelo's assistant Vignola to finish it, but he was not able to. After twenty years Pope Sixtus V gave the job to the architect Giacomo della Porta and the engineer Domenico Fontana. Giacomo Della Porta successfully built the dome. He made some changes to the design, like adding some lions' heads to the decoration because they were the symbol of Pope Sixtus' family. The main way that the dome is different from the wooden model is that it is much more pointy.