Adelaide is the wine capital of Australia, and vineyards have been planted in the area from the very earliest days of the colony (and in fact the oldest urban vineyard in the world is at Marion).
Presently there is a small display vineyard at the National Wine Centre, but I think it would be excellent to have a vineyard for community use somewhere in the Parklands, where the vines could be tended and the grapes harvested by volunteers. An annual Harvest Day would be a great little community event.
A small amount of wine could be produced professionally and sold each year to raise money for charity, or to maintain the costs of the vineyard - imagine the symbolic value of a wine grown & made entirely within the City of Adelaide! This would be really unique at a global level, and I think it's something that interstate and overseas visitors would really embrace.