This vast painting by Tintoretto depicts the Lord washing the feet of his Apostles at the Last Supper. At first sight there appears a peculiarity: A dog occupies the center foreground, while Christ and Saint Peter are way over on the right. But try an experiment: Move so that your head is not in front of your computer but to the right of it, and then from that position look at the image obliquely.
As if by magic, the perspective has shifted. Now Christ and Peter are closest to us, and the central perspective of the painting leads from them to the Supper table and the Apostles who are learning to imitate Christ, and thence to the city (the place of mission), in this case Venice.
The effect is of course stronger in the real painting, because the figures are life size. The painting originally hung on the south wall of the 'choir' of a church, i.e., the space between the congregation and the sanctuary and altar. So the people saw the painting from the position we duplicated in our experiment. In the Prado Museum where the painting now hangs, it is on the right wall of the main hall, so visitors to the museum get this view as they approach the painting.
Tintoretto was always teaching the truths of the Christian Faith in his paintings. Here he reminds us that we must let Christ cleanse us of our sins before we partake of His Supper; and that once we are nourished with His Body and Blood we are to imitate His example of service.