I think you're going to want a system of nested spheres. Each "layer" of nested sphere has a pressure gradient. With Martian gravity (~0.4G if i recall correc

I think you're going to want a system of nested spheres. Each "layer" of nested sphere has a pressure gradient. With Martian gravity (~0.4G if i recall correctly) and geodesic designs you can make really big structures (tens of kilometers).