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We perform a large-scale topology mapping and geolocation study for China's Internet. To overcome the limited number of Chinese PlanetLab nodes and looking glass servers, we leverage unique features in China's Internet, including the hierarchical structure of the major ISPs and the abundance of IDC data centers. Using only 15 vantage points, we design a traceroute scheme that finds significantly more interfaces and links than iPlane with significantly fewer traceroute probes. We then consider the problem of geolocating router interfaces and end hosts in China. When examining three well-known Chinese geoIP databases, we observe frequent occurrences of null replies and erroneous entries, suggesting that there is significant room for improvement. We develop a heuristic for clustering the interface topology of a hierarchical ISP, and then apply the heuristic to the major Chinese ISPs. We show that the clustering heuristic can geolocate router interfaces with significantly more detail and consistency than can the existing geoIP databases in isolation. We show that the resulting clusters expose several characteristics of the Chinese Internet, including the major ISPs' provincial structure and the centralized interconnections among the ISPs. Finally, using the clustering heuristic, we propose a methodology for improving commercial geoIP databases and evaluate using IDC data center landmarks.