Independent city-states are self-governing cities that operate independently from larger political entities, such as countries or empires. They have their own governments, laws, and often their own economies. Examples of historical independent city-states include Athens and Sparta in ancient Greece, which had their own distinct cultures and political systems. Today, a few modern examples of independent city-states include Singapore, Monaco, and Vatican City. These city-states maintain sovereignty and are recognized as separate nations, despite being small in size. They often have unique political structures and economic systems that allow them to thrive independently.