Forbidden City

From the Super Mario Wiki

Luigi's photograph of the Forbidden City.

The Forbidden City, now called the Palace Museum, is a building located in central Beijing that used to serve as a place for the Chinese Emperors of the Ming and Qing Dynasties to reside. It is one of Beijing's landmarks Luigi visits in Mario is Missing!. During the events of the game, the Gate of Heavenly Peace, an entrance to the Forbidden City built solely for the Chinese Emperor, has been stolen by Koopas, and the City will not reopen before Luigi returns it, for which he is rewarded $1750 plus $2800 bonus.

[edit] Pamphlet Information from Mario is Missing!

The Gateway of Heavenly Peace, Tian An Men, was built in AD 1651. An impressive 110 feet tall, Heavenly Peace is the main entrance to Forbidden City, which has been renamed the Palace Museum. Once the walled estate of emperors, only the Emperor himself was permitted to use Tian An Men -- guards kept everyone else out. Those entitled to visit the City had to use a separate entry. In 1949, the leader, Mao Zedong stood at the Gate to announce the formation of the People's Republic of China, the present day Communist government.