The Bazaar of Tabriz is the largest covered bazaar in the world, and is a UNESCO world heritage site. It's easy to get lost in the maze of buildings and alleys, where you'll find anything, from the Tabriz specialties leather (an abundance of shoe shops can be found here) and intricate silverwork to herbs, beautiful Termeh and of course Persian carpets.
Hang on to whoever you're with to make sure you don't lose each other - or run down by delivery carts and scooters. And don't buy too fast - prices may vary in between shops, and you might find herbs in one shop for a much lower price in another. It helps to have a local at your side at any rate...