Vatican City — World Flags

The story behind the answer

Vatican City is correct because its flag features the papal tiara and the crossed gold and silver Keys of Saint Peter—emblems of papal authority. The yellow and white colors trace back to the Papal States. A quick mnemonic: keys = “keys to heaven” = the Pope = Vatican.

Vatican City is the world’s smallest sovereign state, entirely within Rome, and the spiritual and administrative center of the Roman Catholic Church. It became independent with the Lateran Treaty in 1929. To avoid mix-ups: Cyprus’s flag shows the island’s map, Liechtenstein’s has a crown on blue-red, and Moldova’s has an eagle on a tricolor—none display the papal keys.