One of the rare free museums in town, the original Shanghai Postal Museum in Hongkou well explains the history of the postal service in China. Venture up to the beautiful baroque rooftop to find a sculpted garden with a Romanesque clock tower and one of the city’s best low-level views: looking west up Suzhou Creek and east towards the Pudong skyline with the Art Deco Broadway Mansions in front.
http://www.timeoutshanghai.com/venue/Around_Town-Museums-_Around_Town-Parks__Gardens/995/Shanghai-Postal-Museum.html