How do I model vaulted ceilings in Hexagon?

I have a project in mind I would love to learn how to do in Hexagon. I haven't been able to do much with this program, however. I sure wished I could contact Jack Tomalin because his stuff is fabulous, and the project I have in mind would be right up his alley! Anyway, I want to do a 3D model of the Eastern Gate in Jerusalem for a project I've been asked to do. This gate was sealed by one of the Ottoman Turks about 1530 A.D. The interior consists of a vaulted ceiling with a series of pillars in the center. The Israelis know this structure, if I recall as "the Beautiful Gate". I would like to know how to create vaulted ceilings AND how to properly scale, and texture, the model for use in DAZ Studio. Any help would be greatly appreciated!


Comments
Here is an image of the INTERIOR I have found.
This is the rear of the gate, inside the ancient wall.