If you get to Tabriz, sooner or later you will end up in the covered bazaar some say the biggest in the world. Few years ago we still had two biggest bazaars in the world - the second one being Al-Madina Souq in Aleppo, but what happened to the Syrian one, we all know and shame on all of us for that.
Tabriz is a very big city and the bazaar is not centrally located - it used to lie in the center of the town but as Tabriz became the main trading post between Turkey and Iran, most of the city moved southward. But the bazaar remains the real heart of the city if not of the whole West Azerbaijan. The main entrance is easy to miss, but don't worry you can always use one of the small gates.
What you can expect? A labyrinth-like kingdom where you can find anything you wish. Carpet, gold, spice, perfume, shoes, food, things you need and things you cannot even name - all's there. More than 20 timches (big vaulted halls), hundreds of alleys and thousands of shops. Go there in the late afternoon! And don't be afraid of the crowd! People are very friendly, they are business people but will find time to serve you a cup of tea or coffee.
In the bazaar itself there are more then 20 caravanserais and Friday Mosque with a brick vaulted interior. In the western part of the bazaar you can see some halls and rooms with 15th century walls!
Tabriz is not a very interesting city, but if you're there you should see the ruins of the blue mosque and Azerbaijan museum; there are some Armenian churches too but they're far from being gems of architecture. For 10 euro you can go to Iranian cave city of Kandovan, the trip can be organized by any hotel or tourist information or the museum.