"Inside the citadel was a forbidden city where only the concubines, emperors, and those close enough to them were granted access, the punishment for trespassing being death." (wiki)

Closed to non-islamic visitors for centuries

Lhasa is known as the Forbidden City for its former inaccessibility and hostility to strangers

It included a Forbidden City, where the king and his royal family lived

"Forbidden" (in Beijing's Forbidden City or Imperial Palace), referred to the fact that no-one could enter or leave the palace without the emperor's permission.

"Harar was a fiercely religious city and was a forbidden city (closed to visitors), until 1887"

Ambohimanga was henceforth considered one of the sacred royal hills of Imerina (the Merina kingdom) and was known as a "forbidden city" until 1897.