Please answer a question about the following article about Melbourne:

The Hoddle Grid (dimensions of 1 by 1⁄2 mile (1.61 by 0.80 km)) forms the centre of Melbourne's central business district. The grid's southern edge fronts onto the Yarra River. Office, commercial and public developments in the adjoining districts of Southbank and Docklands have made these redeveloped areas into extensions of the CBD in all but name. The city centre has a reputation for its historic and prominent lanes and arcades (most notably Block Place and Royal Arcade) which contain a variety of shops and cafés and are a byproduct of the city's layout.

Which edge of the Hoddle Grid fronts onto the Yarra River?
southern