Zhong Ma

 was a fortress used by the Japanese prior to World War II. They used it to conduct experiments in biological warfare.

Mai Ling was a captive in Zhong Ma. The Seventh Doctor and Edward Grainger were briefly imprisoned there when they arrived to rescue Mai Ling. While there, Edward was deliberately infected with the Bubonic plague. The three were able to escape. According to the Doctor, the people involved with the experiments would never be called to account for their crimes. (PROSE: Log 384)