Regardless of how much you read, stories you hear or pictures you see, Place Jemaa el Fna must be experienced first hand to really understand what it is about. The musicians, the snake charmers, the fresh orange juice and the stalls of super fresh food at night (all of them are great, just pick one where there is a lot of people). Try a Merguez sandwich and ask for spicy sauce. Superb!
It takes more than a few visits to take it all in. It is preferable to stay at Riad in la Medina to be able to visit Jemaa el Fna often.