Demon City
Existing somewhere within Makai, Demon City (The City of Ghosts and Apparitions in the English dub) is ruled by the Four Saint Beasts, Suzaku, Seiryu, Byakko, and Genbu. Since the City is such a large threat to Ningenkai, Reikai created a barrier around the world to prevent any of the inhabitants from ever leaving, thereby protecting everyone on Earth. However, in the Yu Yu Hakusho series, the rulers of Demon City eventually grow tired of this, and attack Ningenkai in order to gain their freedom.