The cropped image above is from Raphael's Fresco The School of Athens.
The Lyceum had been used for philosophical debate long before Aristotle. Philosophers such as Prodicus of Ceos, Protagoras, and numerous rhapsodes had spoken there. The most famous philosophers to teach there were Isocrates, Plato (of The Academy), and the best-known Athenian teacher, Socrates. In addition to military training and educational pursuits, the Lyceum also housed Athenian Assembly meetings before the Pnyx became the official meeting place in the fifth century BCE. Cult practices of various groups were also held at the Lyceum