Beijing ≠ Forbidden City. Beijing is China's capital city (21M+ people). The Forbidden City is a 72-hectare palatial complex within Beijing—former imperial palace of the Ming (1368–1644) and Qing (1644–1912) dynasties.
Now called The Palace Museum, it houses 1M+ imperial artifacts. The name "Forbidden" (紫禁城, Zǐjìnchéng) meant commoners couldn't enter without permission.
Beijing contains the Forbidden City—like Manhattan contains Central Park. One is the container; the other, the jewel.