Between 10am and 4pm, more than 200 stalls will offer a range of wares from clothing and crafts to jewellery and produce.
Thousands are expected to converge on the central city as the "Summer Fun 09" event is more than just a street market.
Runners will race the town hall clock chimes around the Octagon at 10am, entertainment for children, including a bouncy castle, will be provided and an international stage will feature a multitude of cultures.
Shrek and Fiona, characters from the movie Shrek, will take centre stage, every 45 minutes, starting at 11.30am, to entertain the crowd with love songs on Valentine's Day.