This book provides a comprehensive overview of twin and border cities across the world. Drawing on examples of both internal and cross border twin cities, it explores the constant and changing features of twinned communities over time. The chapters explore a variety of urban formations including independent cities that are proximately located, cities that have merged over time, cities divided by conflict or treaty, and cities that are twinned across different countries. The relationship between cities and municipal and international borders is explored, as well as the extent to which these are changing or remaining constant in the context of conurbanisation, Europeanisation and globalisation.