Flags of the World | Vatican

Postcard
The flag of Vatican City was adopted on June 7, 1929, the year Pope Pius XI signed the Lateran Treaty with Italy, creating a new independent state governed by the Holy See. The Vatican flag is modeled on the 1808 yellow and white flag of the earlier Papal States.

The flag is probably one of the smallest. With height to width 1:1 it is actually a square.