Pandarenboy said:
It's a different dimension created by Juha Bach, there's no way for Shinigami to notice it
Was it a dimension? I read only 'shadows', but I'm not sure about that.
but:
1) 1000 years
2) Urahara, Mayuri, Genryūsai Shigekuni Yamamoto and probably others hasn't noticed?!
3) Shinigami controls Dangai, Urahara can create 'gate' to Hueco Mondo and one of Vaizards could seen through Aizen's halucination