A city-state is a city that has its own sovereignty, meaning that it is its own country. There were many important city-states in ancient Greece. Nowadays, cities may have differing degrees of self-governance. In order to be considered a city-state, a city must govern itself independently, by regulating its own taxes, or having independent representation at the United Nations.

• In Ancient Greece a polis was a city-state
  • Athens
  • Sparta
  • Corinth
  • Thebes

Sorted in order of area size.

• Singapore was a British colony till 1959. In 1959, it achieved autonomy in internal matters. Between 1963 and 1965, it was part of Malaysia. Singapore was removed from Malaysia on 9 August 1965 and became independent.
• The second smallest country in the world, Monaco is entirely urban, because all its territory of only 2 square kilometers is built-up.
• The smallest country in the world was created in 1929. The Vatican City is an enclave completely surrounded by the city of Rome, Italy, and is the headquarters of the Roman Catholic Church.