How to create curved/rounded soffit with spire roof?

[LanaInteriors]

Hi all, 

I'm trying to accurately recreate this soffit/ceiling in my plan. On one side of the room, it's a vaulted ceiling with lots of beams, and the other side is this curved half-moon soffit that meets at the base of the vault. 

I've tried 3D solids, half walls, soffits, attic walls, and none of them are achieving what I need. In one of the photos, you can see the spire on the roof with the windows. 

I'm really just trying to achieve something as close to the photos as possible, as I'm building out the existing space.

Any help would be appreciated. Thank you!

[ericepv]

It would help if you post your plan. Also, you should re-post your request to the 'General Q&A' forum, this forum is for sharing  your solutions to problems.