Kalgan
Fortified trade city on the border of Inner Mongolia and Hebei, a key political and commercial hub in the early 20th century.
Kalgan (present-day Zhangjiakou) sat astride the historic caravan routes linking China proper to Mongolia and Russia. Through the early 20th century it served as a major wool and tea trading post and, at various points, as an administrative center for competing Chinese, Mongol, and Japanese-aligned authorities.