Khaqani Park, also written Boostan-e Khaqani, is a modest urban park named for the 12th-century poet Khaqani Shirvani. It sits a few blocks east of the bazaar and provides a useful break from the dense old town — there are benches, a few flowerbeds, and the usual gathering of older men playing chess.
It's small and easily covered in 15 minutes. Combine it with a visit to the nearby Blue Mosque or use it as a meeting point if you've got separated in the bazaar.