A city-state is a sovereign state that consists of a city and its dependent territories. Historically, this included cities such as Rome, Athens, Carthage, and the Italian city-states during the Renaissance—but today only a handful of sovereign city-states exist, with some disagreement as to which are city-states. A great deal of consensus exists that the term properly applies to Singapore, Monaco, and Vatican City. A number of other states share similar characteristics, and therefore are sometimes also cited as modern city-states. These include Malta, Bahrain, and San Marino which are microstates with high population densities; as well as Qatar, Brunei, and Kuwait, each with an urban center comprising a significant proportion of the population, though all of them have several distinct settlements and a designated or de facto capital city. Several non-sovereign cities enjoy a high degree of autonomy, and are sometimes considered city-states. Hong Kong and Macau, along with...