Istanbul's Spice Bazaar is (surprise, surprise) in the Bazaar district. It is not far from the Galata Bridge and the access points for Bospherous Cruises. The nearest tram stop is Eminonu. The Bazaar is all mostly undercover and much smaller than the Grand Bazaar and less confusing. It seems to just run one row up and down and another across. The centre 'cross-roads' can be a bit of a nightmare to get through with loads of people trying to squeeze through, and the narrower exits can also be a challenge. I think we were going along as people were cutting through on their way home from work as the passageways were busy, but the stalls, not so much.
The building is Ottoman (17th century) with high domed ceilings, although I can't say I found it particularly attractive. It was built as part of the New Mosque, which is next door.
One of the first stalls I saw (entering by the New Mosque entrance) was a handmade soap stall and they had scores of pretty, fragranced soaps and I was tempted and in retrospect wish I had bought a a few as gifts, as I did not see more again. What you will see lots of are dried fruit, nuts, herbs, spices and non-food items like ceramic jugs. Ninety percent of the stalls here are food related however. For other gift ideas this is a good place to purchase Turkish Delight and other sweet products like nougat in any flavour or version you can think of. I believe on the other side are some outside stalls selling cheeses and flowers, but we didn't investigate this area.
If you are looking for food related gifts or herbs and spices then this is a good place to come. Stallholders are happy to let you try samples, and many will call you over and try and engage you in conversation. However, it is all good natured and there is no hard sell. Prices didn't seem to be particularly cheap and I didn't see too many locals indulging in purchases, I expect they know better and cheaper places.
The Bazaar is free and open seven days a week from 8am to 6pm (slightly reduced hours on Sunday) and should take you no more than half an hour to wander and browse
The Spice Bazaar is smaller than the Grand Bazaar and set slightly apart from the main area around Sultanahmet Square, but it's definitely worth the walk/ extra tram token.
The inside area is good for spices, fragrances, ceramics and little knick-knack type jewellery (I was travelling with a teacher who wanted to bring back little activity rewards for her pupils and got several of them here). Being much larger the Grand Bazaar has a wider range of stuff on sale e.g. if you're looking for carpets this is the place to start.
The most interesting bit of the Spice Bazaar is outside the front. There are lots of cafes for Turkish coffee and apple tea on one side and a flower market on the other selling a wide range of flower bulbs, vegetable seeds, leeches and birds. Some of these things are not practical to buy if you're flying home, but it's an interesting place for a walk.
The Spice Bazaar is also very close to the Bosphorus ferry, so after shopping you can go sit by the water's edge, or catch a boat across to the Asian side of the city.