Tree houses are a common play area for children in rural areas all across the world. Though most of these sparse houses are limited in size and usually one to three rooms, not all tree houses fit this mold. The largest all wood tree house in the world is built amongst the lime trees in Northumberand County, UK. The tree house is 6,000 square feet and includes cottages, shops, a restaurant, play area and walkways. There is even a deck area and rope bridge behind the house. Talk about luxury…in a tree!