Premise: The Tuancheng Fortress or Tuan Cheng Fortress (Chinese:  團城演武廳 ,  团城演武厅 ,  "Tuánchéng Yǎnwǔtīng",  "Round Wall Fortress") is a historic 18th-century fortress located near the Fragrant Hills in the Haidian District of Beijing, China. Today, the fortress is a national museum and is also known as the Tuancheng Exhibition Hall.
Hypothesis: the Haidian District of Beijing is a very large city.