I first tried to make the stone arch with drawing only one terrain - Surprisingly (to me at least) this was more difficult and less sastifying. The I simply did medieval building block of sort. For economy I reseted and resize the terrain down to 64x48, but I could (and should) have done still less since its just about making square like stones. To draw in the terrain editor : cranking the /Softness/ slider to its max, for a rightangled "slope" (ie : the sides and top/bottom of the each block. Using the /Minimum/ and /Maximum/ buttons is needed to have a flat "face", which can then be sightly bumped here and there with 2 or 3 /Terrace/ effect and 5 or 6 /Grit/. The rest was just masonnery - litteraly! I put the center-top terrain stone first, above and inside the arch (made from a cube bolean-diff with cyl+cube#2)the duplicated this block on the side with an quick redrawing in the terrain editor to reduce the sides angles (from a front viewpoint). If you look at the picture I guess this will be clearer, and one can easily see that once I got an vertical half of the arch I simply duplicater each stones to make the other side. This kind of "mirror" was halas not possible with a group. That's why once an objet is duplicated : simply add or remove an "-" (minus) sign in the parametter box of the necessary position axis (in 'X'for me); do the same for a rotation axis since each block is successively rotated as you can see. In short, i first rotate and pose manually, then modify only the positive/negative sign in parametter for the second, "twin" object. Well, I'm not sure Im clear enough, but I hope. :-) Herv