I've used lego for scenery (it's when you're posing your minis in a lego building as a 42 year old that you feel like you've really accomplished something with your life) but if you're going to do anything bigger than simple rooms and corridors, you're looking at spending a bunch of money. Anyhow, lego don't fit evenly into inches, but I find a three nub by three nub square is close enough. I only did it a couple of times because building as you go takes much longer than drawing on a battle mat, and people would get bored.