The ends of the chapel are closed by flat walls, against the western of which is raised the altar.
When Michelangelo was called to paint here, he found both sides of the building, just below the windows, decorated in fresco by Perugino, Cosimo Rosselli, Sandro Botticelli, Luca Signorelli, and Domenico Ghirlandajo.

These masters had depicted, in a series of twelve subjects, the history of Moses and the life of Jesus.

Above the lines of fresco, in the spaces between the windows and along the eastern end at the same height, Botticelli painted a row of twenty-eight Popes.
The spaces below the frescoed histories, down to the seats which ran along the pavement, were blank, waiting for the tapestries which Raffaello afterwards supplied from cartoons now in possession of the English Crown.

At the west end, above the altar, shone three decorative frescoes by Perugino, representing the Assumption of the Virgin, between the finding of Moses and the Nativity.

The two last of these pictures opened respectively the history of Moses and the life of Christ, so that the Old and New Testaments were equally illustrated upon the Chapel walls.