Ok, not technically my first time, but in the past I've just used sci-fi bits here and there to detail buildings, but this time a buddy gave me a bunch of fieldstone bricks he had cast and I built a variety of stone walls/fences for my medieval village. Pics, molds used/needed, and painting process here:
http://chicagoskirmish.blogspot.com/2015/05/fieldstone-walls-with-hirst-arts-blocks.html
After building 20 of these I determined that I probably don't have the patience to cast bricks myself, but I certainly do enjoy building with them. I worked up a couple of other items with some leftover bricks that I'll post up later.