vis error

Your map contains too many vertices. Your brushwork is too complex, and some of it should be turned to models if you intend to keep it as detailed.

Either remove it or rework it so it's less detailed. Can you post a hammer screenie of said architecture? That would help knowing how much work you'd have to put in it.

The high number of vertices could also be caused during the bsp parts of the compile if you haven't made proper use of func_detail.

Anyways, as Furyo says it would be very interesting to see a picture of two of your map. Usually max_map_verts is not anything you need to bother about unless that you are making an extremely large and detailed map. Usually there are other reasons behind the error.