Hello everyone.

We know for a fact that Nirn is spherical, like earth. However any sphere by definition has a diameter and a core. The earth's core is divided in inner and outter core, the inner being rigid and the outter being solid, and both being very hot.

So, what could Nirn's core be like? Could the Clockwork city be located there/be the core?

Yep, Nirn's underground holds the metaphysical clockwork that keeps it together. The Clockwork City, and more accurately the Wheels of Lull are what sit at the center. Hence why there's conflicting reports of where it's located, because it's actually located beneath everything.