This fantastic little igloo-style tree-house was created by two wonderful shopkeepers at the Des Moines Renassaince Faire. When I spoke to the owner of the shop she said that they had planted the trees last year (the Faire has a permanant spot here in DM) and when they came back this year it was like this. So this picture represents a year of growth. Imagine what it would be like in 5 years! My children and I are already very excited about planning this for a project next spring. Or perhaps even now...we can't wait! It is very simple. You have to choose a tree with flexible branches and trunk. Plant it when young, but no so young that it takes "forever" to grow. I would recommend starting with 5 foot high trees at the very least. Once you plant the trees in a circle you can build up the bricks around them in a circle or you can choose just to surround the based of each one to protect it. Of course choose trees that grow quickly (your local nursery can help you with this) and notice how they planted vines around the bottom of each tree? This is to fill in the spaces that the leaves and branches don't for the tree house. Choose something appropriate for your area but not something that will grow faster and take over the tree.