User blog comment:Zippertrain85/The reasons why Serana is not from the First Era./@comment-3186827-20130514090704/@comment-9062114-20130514234405

Possibly someone in High Rock or Skyrim. Once the Empires started becoming established in Cyrodiil they could start trading. They could get new rocks and design techniques that way. Also, the Breton race would exist and they would have insiprations to make buildings look that way. Going across the Jerall Mountains wouldn't be easy, but they could still do it.

Again, I'm just using reasoning to assume that it was probably the ancient Nords who built it.

This is a flawed argument because the Soul Carin is a plane of Oblivion. While Nirn is a mortal plane. The Ideal Masters can make it look exactly how they want it to look. It doesn't need to have things like material. On a mortal plane that isn't the case though. I bet evan the College of Winterhold had to have some materials, and they just put them together with magic.