Which pope commissioned Michelangelo's first Vatican project and what was the project?

Giuliano della Rovere or Julius II as he came to be known after
he became the Pope between the years 1503 and 1513 was a fine patron of the arts. He commissioned
Michelangelo for his first work for the Vatican which was to build a tomb for the Pope in 1503.
But the building of the tomb was interrupted by a project for the Sistine Chapel. Michelangelo
had to paint twelve figures of the apostles and decorate the ceiling. In due course the artist
came to have a choice to paint whatever he liked and over four years painted more than 300 of the
finest works of art on the Sistine Chapel.