Antonio da Sangallo was the architect employed upon this work, which advanced slowly until Alessandro Farnese's elevation to the Papacy.

He then determined to push the building forward, and to complete it on a scale of magnificence befitting the supreme Pontiff.

Sangallo had carried the walls up to the second story.

The third remained to be accomplished, and the cornice had to be constructed.

Paul was not satisfied with Sangallo's design, and referred it to Michelangelo for criticism -- possibly in 1544.