Istanbul's Grand Bazaar is larger than the Spice Bazaar. It has many many places to spend your Turkish lira. It's also old, with parts of the bazaar dating back to the mid 1400s.
The entrance to the bazaar is just an arched doorway facing a street. Inside is a maze of enclosed streets lined with small shops. Those selling similar things, say gold or women's dresses or ceramic dishes, appear together, which can either make comparisons easy or lead to decision paralysis.