West Lake or Xi Hu (西湖) is a world famous fresh water lake known for it's picturesque scenery.
On any given days, the lake is full of old style cruise boats doing the tourist rounds:
The area around West Lake is full of beautiful scenery, with huge willow trees, and mountains dotted with pagodas in the distance:
Giant Koi fish hanging out for a feed
A lot of people hire the red bikes and cycle around the areas near West Lake, which I think is quite a good way to explore the area (maybe not so much in the heat though!)