The most famous philosophers of ancient times move within an imposing Renaissance architecture which is inspired by Bramante's project for the renewal of the early Christian basilica of St Peter. Some of these are easily recognizable. In the centre Plato points upwards with a finger and holds his book Timeus in his hand, flanked by Aristotle with Ethics; Pythagoras is shown in the foreground intent on explaining the diatesseron. Diogenes is lying on the stairs with a dish, while the pessimist philosopher, Heracleitus, a portrait of Michelangelo, is leaning against a block of marble, writing on a sheet of paper. Michelangelo was in those years executing the paintings in the nearby Sistine Chapel. On the right we see Euclid, who is teaching geometry to his pupils, Zoroaster holding the heavenly sphere and Ptolemy holding the earthly sphere. The personage on the extreme right with the black beret is a self-portrait of Raphael.