In Tehran, as I know, Manuchehri boulevard is the center of antiques and hands crafts galleries. You can take Metro to "Sa'di station", once you step out of the station, walk down the street towards west (the mountains are located at north of the city, so you can know which direction would be the west..); after a few hundreds of meters you will reach "Istanbul crossroad" (In Farsi: Chahar rah-e- Estambol), where you can see British embassy, Turkish embassy and Melli Bank around you. Walk up the street on your right (towards north) for some tens of meters. The first major street, after one block, would be Manouchehri boulevard. From Istanbul crossroad, all the way towards Manouchehri, there are full of such shops and galleries. Some good ones might not be easily visible or accessible from main roads.