Xiangming Chen and Curtis Stone INTRODUCTION What happens to border cities in this age of widespread urbanization, intensified globali- zation, and accelerated mobility? How does urbanism manifest itself and change in previ- ously isolated and recently opened border regions? In what ways do rapid growth and greater opening of border cities affect local governance and everyday life? We are living in a world where cities have become more diverse and fluid than ever before. A small number of heavily studied cities like New York and Shanghai, the two largest and most cosmopolitan cities in the United States and China, respectively, exert and project power- ful global influences due to their size, geographical location, and highly developed and diverse economic strength. At the same time, many small cities have gained stature through accelerated growth and new global connections despite their less advantaged locations, as in frontier regions. We know a lot more about the former type of cities than the latter, which act more as urban gateways to two or more connected countries. As border cities become more and more important and even central to understanding such critical urban topics as mobility, despite their relatively small size and peripheral loca- tion, they deserve our renewed attention and creative inquiry. Two salient, and somewhat paradoxical, features of border cities quickly stand out. On the one hand, they are small in size, located in underdeveloped and vast ‘frontier’ regions, and somewhat isolated. On the other hand, the international borders near these cities are more fluid than fixed, and they are caught up in the uneven trans-boundary distribution 26 Rethinking Border Cities: In-between Spaces, Unequal Actors and Stretched Mobilities across the China–Southeast Asia Borderland BK-SAGE-HALL_BURDETT-170083-Chp26.indd 478 05/07/17 7:01 PM In The Sage Handbook of the 21st Century City, edited by Suzanne Hall and Ricky Burdett. Sage, 2017.