The Royal Botanic Garden is one of the nicest spots for a market I've yet seen. Once you've finished wandering amongst the stalls take the chance to meander around the gardens which in themselves deserve at least half a day of exploring.
At the market there is an interesting range of objects on sale from around 100 stalls including:
"jewellery, garden ornaments, handbags, fashion, plants, artwork, sculpture, photography, healthy produce, to name a few."
Most of the stalls are garden themed in some way which is a nice touch. There are also a number of good gourmet food stalls in case you get the munchies.