Best way to make a very large building as a map?

I’m wanting to make circular building with a radius of about 700m and probably 10-20 stories with a lot of repetitive rooms and halls in Unreal Engine (it would be a completely indoor map but would have windows on the outer walls if this is relevant).

What is the best way to go about this?

Should each floor be a different level, should it be divided up into quadrants per floor or even smaller subsets?

Is there any way to do simple placement of the repetitive rooms? (initially I tried importing entire rooms of roughly 27,000 swft as meshes but that seems to wreak havok with the lightmapping and collission causing it to run really slow in spite of having relatively simple meshes [only the outer walls of 6-sided polygons were included])

Additional tips in relation to building on this scale would be appreciated as well.