There is nowhere on Earth like the souks of Marrakech. I'd been to the souks of Egypt and Turkey before, but those of Marrakech took it to a whole other level. They're basically a small city in their own right! The souks are actually a small neighborhood of the Marrakech Medina which, realistically, seems like one massive souk itself.
The souks are divided into several sections, each with a specialty: wood-working, clothes, lamps, metal-works, jewelry, leather-goods, spices, etc. You'll hear people on the street telling you about a "special Berber market" but don't buy that. It's a ruse. Just keep exploring and you'll find some amazing things. I'd especially suggest the back alleys of the leather and metal-working souks where you can see the workshops and the people going about their daily lives.