There were a lot of unique settings in 2nd edition D&D: Planescape, like you mentioned. Spelljammer, which was like D&D IN SPACE! Al-Qadim, an Arabian Nights style setting; Maztica, an Aztec-like setting; Kara-tur, an East Asia-like setting; Council of Wyrms, where you played PC dragons in a world ruled by the United…