In a sentenceA frozen continent at the top of the world with a citadel on it, and everything wrong with the present age started there.
The frozen northern continent. Arthas Menethil sailed here, burned his ships, took up Frostmourne, and lost his soul. Ner'zhul crashed here as the Lich King and was frozen into the Icecrown Glacier.
Also here: Ulduar (a Titan complex, rumored only), the Nexus (Malygos's seat), the Frozen Throne, and Naxxramas — which is still hovering here, not over the Plaguelands.
