Bei Wenquan Park is one of the best getaways in Chongqing: It's still in the city and easy to reach by train (take line six). The park has hot springs, and, like most natural hot springs, they're rumored to cure various ailments. They certainly cure the Chongqing winter blues. The springs' communal changing area is an experience, so feel free to pay one of the resorts to use their fancier facilities.
The park is huge, with many other attractions. It has four palaces, an ancient temple, and romantic tree-lined trails as far as the eye can see.