This is the Pope Julius II by Raphael, painted in 1511. The portrait shows a careworn expression on the Pope's face, which may be explained by his continuing precarious state of health. He was still recovering from a serious illness brought on by the loss of Bologna to French troops.
The two golden acorns on the chair allude to his family name, della Rovere. The reflections in their gleaming surface reveal that Julius was seated opposite a doorway in a narrow room lit by a mullioned window.
Raphael's portrait was enormously influential and became the model for ecclesiastical portraiture over the following 200 years. It was displayed on 12 December 1513, after Julius's death, in the Roman church of Santa Maria del Popolo.
Pope Julius II hangs in The National Gallery on Trafalgar Square, London — free to enter. Point your phone at any artwork there and audioguide.london plays a free audio guide in six languages — no app download needed.