There's something about a treehouse that appeals to all of us. Maybe it's the view, or getting close to nature, or reliving childhood memories. There are many ways to enjoy treehouses, no matter what age you are.
A Treehouse Protest
Beginning in 1997, Julia Butterfly Hill spent two years in a treehouse, 180 feet up in a tree named Luna to protest old-growth logging. Her treehouse was only a 6x8 foot tent, but she had plenty of visitors and conducted interviews via cellphone. Luna was estimated to be somewhere between 600 and 1,000 years old! Hill's protest drew the support of Earth First! and other environmental organizations. Hill finally came down from the tree on December 18, 1999 when Pacific Lumber Company agreed to spare the tree and a three-acre buffer area. In 2001, the tree was damaged by someone with a chain saw who cut a 32-inch deep gash around the trunk. Guy wires were added for support, and the tree survives today.
The Treehouse as Art
The Steampunk Tree House is a 30-foot-tall interactive work of art first exhibited at Burning Man. It is made of recycled wood and metal, and outfitted with steam pipes, which can exude puffs of steam when needed. There are solar panels included, which power LED lights. The Steampunk Tree House will appear at the Coachella 2008 music festival next weekend and the Stagecoach music festival in May, both in Indio, California.
Hotels
Permanent Homes
If you want to live in a treehouse all the time, there are ways to do it. Finca Bellavista Rainforest Village is a permanent community of treehouses at the base of a rain forest mountain in Costa Rica. The goal of the community is to preserve rain forest acreage and promote sustainable living arrangements.
Grownup Retreats
For Kids
Kevin McKinney built a treehouse for his two daughters on top of an 8 foot wide Giant Redwood stump. The house has a cantilevered porch, observation deck, sink, closet, and interior stalactites!
Ground Level Tree Bar
A Baobab tree in Limpopo, South Africa is so big that it's been made into a bar! The tree has a 155-foot circumference and is hollow. The bar can seat 15 people comfortably, and once held 54 people (although not comfortably). Baobabs begin to hollow out at about a thousand years of age; this tree is estimated to be 6,000 years old. When owners Doug and Heather van Heerden set up the pub in the late eighties, they found artifacts indicating that Bushmen and Dutch pioneers had been inside, and had possibly lived in the tree.
Tree Tent
The Treepee is a tent that hangs from a tree! You can use it as a trampoline that you can't fall out of (unless you leave the door open), or a swing. Tether the corners to the ground for more stability. If you hang it high, use the pulley that comes with it to haul up provisions. The floor is much softer than the ground, for either sleeping or sitting.
This is just an overview of different kinds of treehouses. You can see quite a few more in the articles Incredible Treehouses and Universally Accessible Treehouses.