Kala Temple was the final pure land of Buddhism back then.
Ksitigarbha thought that Alex was the future Lord Buddha, so he left the legacy to Alex. At the same time, he also gave Alex control of the entire Kala Temple for his usage.
As the saying in Buddhism went, “To see a world in a wildflower and a Bodhi in a leaf.”
Kala Temple did not exist in any space on Earth, but it came from another realm.
The teleportation portal at the bottom of the large lake back then was just an ancient space t