Around 4km across, Chengdu's downtown area contains a warped grid of streets enclosed on three sides by the black, malodorous, canal-like Fu and Jin rivers, themselves surrounded by an ever-increasing number of ring roads. Broad and lined with plane trees, Renmin Lu is the main thoroughfare, divided into north, middle and south sections. It runs from the main train station on the northern edge of town, through the city centre and down past a knot of hotels before crossing the Jin River and heading out to the South train station and routes to the airport. The centre itself is marked by a large, grassy public square in front of the city's ponderous Exhibition Hall , from where Renmin Dong Lu heads east to Chengdu's entertainment and shopping precincts, while Renmin Xi Lu points west towards Renmin Park.