I get asked a lot how I start a diorama -- my preference is to use playscale or Barbie doll houses -- I like the proportions, I can stack them and I can usually cut out windows or doors to suit my needs.  I have many, many of these dollhouses.  They are very modular so I am constantly rearranging them. You can usually find them very cheap on Craigs List (Ebay tends to be pricey because they are heavy and cost a lot to ship).  I don't typically care about the furniture that these houses tend to come with so I am happy to buy a dinged up or stripped down one.  I am working on a city concept -- stores, offices, restaurants, homes with a green space in the middle.  Here are some of my "towers:"