A city-state is a small, independent political entity that consists of a city and its surrounding territory. It operates like a sovereign nation, with its own government, laws, and often a distinct culture. Historically, city-states were common in regions like ancient Greece, where cities such as Athens and Sparta functioned independently. City-states can also be found in modern times, with examples like Singapore and Vatican City. These entities maintain their own political systems and economies, allowing them to govern themselves without external control. City-states often have unique identities shaped by their geography and history.