Brick-built Rocks is a very useful technique, it is quite piece consuming, but in the end when it is finished it looks better than if you just used the big Lego rocks. In my creation, The Castle With Many Techniques, I used a brick-built rock that I made. I also was able to add a dungeon inside the rock. Brick-built rocks are quite realistic, and I think that it is worth the pieces it takes to make one. Brick-built rocks are being used more and more in Lego creations.