City rights are a feature of the medieval history of the Low Countries. A liege lord, usually a count, duke or similar member of the high nobility, granted to a town or village he owned certain town privileges that places without city rights did not have.
In Belgium, Luxembourg, and the Netherlands, a town, often proudly, calls itself a city if it obtained a complete package of city rights at some point in its history. Its current population is not relevant, so there are some very small cities. The smallest is Staverden in the Netherlands, with 40 inhabitants. In Belgium, Durbuy is the smallest city, whilst the smallest in Luxembourg is Vianden.
When forced by financial problems, feudal landlords offered for sale privileges to settlements from around AD 1000. The total package of these privileges comprises the city rights.
Such sales raised (non-recurrent) revenue for the feudal lords, in exchange for the loss of power. Over time, the landlords sold more and more privileges. This resulted in a shift of power within the counties and duchies in the Low Countries from the aristocracy to the bourgeoisie, starting in Flanders. Some of these cities even developed into city-states. The growing economic and military power concentrating in the cities led to a very powerful class of well-to-do merchants and traders.