twin town

Fingerposts in Oskarshamn, Sweden, showing the direction from the post to each of the city's twin towns A sister city or a twin town relationship is a form of legal or social agreement between two geographically and politically distinct localities for the purpose of promoting cultural and commercial ties. While there are early examples of international links between municipalities akin to what are now known as sister cities dating back to the 9th century, the modern concept was first established and adopted worldwide during World War II.

Origins of the modern concept