I've been using some hirst arts oieces lately for some of my projects. there are alot of good items available including alot of Egyptian type structures, and other gothic pieces.
Here is their website:
http://hirstarts.comBUt I found a guy on ebay, who is liscensed to sell castings from the molds. He does a good job with them and the castings are very clean:
http://stores.ebay.com/WyrmCast-ModelsI have my second set of field stone items on order, and then after that I will have some of the egyptian items to do.
Using hte pieces is like using Lego or similar stacking blocks without the pegs. the pieces are very well designed, and go together very easily. I made the entire ruined gothic tower in one evening.