This is the vibrant centre of Marrakech & comes alive in the late afternoon & through the night.
I suggest seeing it from 2 angles - firstly down in the thick of it & secondly looking down on it from above from one of the many restaurant terraces that surround it.
It's a great place to take pictures - but expect to tip performers/snake charmers if you take their picture.
If you have the time experience the square both before sunset & after - while it's still light it's good to wander over to Koutoubia mosque & then have a look at all the weird & wonderful food being cooked by skilled chefs on makeshift grills. After dark the fire eaters & other performers seem even more surreal!
Try & hit one of the terraces early - everybody - tourists & locals want a ringside seat at sunset & the terraces get very busy. Get there half an hour before sundown & sip a traditional mint tea - a great soothing contrast to the fray below.