Harvest the Information from Multimedia Big Data in Global Camera Networks Many network cameras have been deployed for various purposes, such as monitoring traffic, watching natural scenes, and observing weather. The data from these cameras may provide valuable information about the world. This paper describes the unexplored opportunities and challenges to harvest the information in the global camera networks. A cloud-based system is proposed to harvest the information from many cameras in an efficient way. This system provides an application programming interface (API) that allows users to analyze the multimedia big data from many cameras simultaneously. Users may also store the data for off-line analysis. This system uses the cloud for computing and storage. Experiments demonstrate the ability to process millions of images from thousands of cameras within several hours.