There are a number of cities which have been divided legally or de facto by claims from two or more nations of sovereignty over the separate parts: such as Berlin, Jerusalem and Nicosia. Cities like Belfast and Beirut have been divided by hostile religious factions engaged in mutual murders and activities; some bilingual or multilingual cities may have formal or informal language zones or show commercial preferences for one official language above another, giving rise to considerable tensions, as exampled in Montreal, Brussels and Miami. Some governments may have a federal district whose residents have one set of laws and advantages but they are situated within a larger metropolitan region with other local ordinances, taxes and amenities, such as happens in Washington and Canberra. Considerable conflict arises because of disparities between these areas. On a smaller scale, university towns pose the adversity of 'town versus gown', not unlike towns in which there is one major supporting industry where interests of the town corporation and the business corporation do not always coincide.
The origins of cities, as recorded in the histories concerning Lycurgus, Solon and Numa for example, show that they were inhabited from the beginning, if not created, by confederations of tribes, clans or classes. Thus cities were, from the start, frequently ethnically and economically pluralistic. Jerusalem too had its Hebrews, Jebusites, Hittites and others, as well as classes of priests, scribes, nobles, merchants, farmers, artisans and slaves. Cities represent the opportunity to form the nucleus of nations by bringing diverse elements into cooperation; to be divided is unnatural.