NURBS Collosseum

I've been getting back into my cgi work and have started learning quite a bit about modeling with nurbs. At the moment i am modeling a collosseum (although the renders I am posting my not just yet ressemble one). As it stands I have currently sculpted two pillars, and archway (from the archway I have lofted the wall section). I have also been spending some time making some detail for the inside of the arch, however Ive hit a bit of a brick wall with the birail tool and for some reason that neither I nor google can work out it is refusing to work. Just sitting around randomly changing settings wasnt getting anywhere so I decided to continue modeling,if the tool starts working or I find another way to make the effect I am after (I think using the animate sweep tool might well do it) then the detailing will be added. Also I need to got throught and match up some curves as shown up in the renders by the black gaps. Anyhow back to work.