This dynamic international collection provides a comprehensive overview of twin cities on administrative and international borders across the world. Drawing on contemporary and historical examples, it documents constant and changing features of twinned communities over time. The chapters explore a variety of urban formations including independent cities located side-by-side; cities that have merged over decades or even centuries and those projected to merge; cities partitioned by treaties and cities duplicated in pursuit of better security, intensified trade or both between neighbouring countries. From Europe to Africa, North America to the Middle East, South America to Asia, this book focuses on relationships between cities, citizens and municipal/international borders. A cartographical contents and editorial commentary guide readers through diverse contributions. The authors ask how far cities are changing or remaining constant in the context of conurbanisation, Europeanisation and globalization. The book provides a glimpse into the variety of roles twin cities can play globally: from laboratories of integration and para-diplomatic actors to economic and cultural brokers. This is a valuable, engaging resource for researchers in the fields of geography, urban studies, border studies, international relations and global development. It will be of great use to individuals involved in twin-city initiatives and general readers.