The ultimate outdoor room just may be in the canopy of a magnificent tree, writes Elizabeth Wilson. Imagine this: you're lounging on a day bed in dappled sunlight, with only the swish-swishing of rustling leaves and trilling birdsong as your soundtrack. You peep out the window and see the world stretching out in front of you. You roll back onto your bed and wonder whether you're awake or dreaming. In the words of Alain Laurens, you feel "between earth and heaven". "When you're alone in your treehouse and you're seeing the view, you have something more. It's magical. It's an incredible world up there," says Laurens. And he should know. Since leaving his job in advertising 10 years ago, Laurens has pursued his childhood dream of building "little houses in the sky". But these are not children's playhouses. Rather, they are wondrous miniature cottage retreats for grown-ups. Laurens' company, La Cabane Perchée, based in the south-west of France, has built treehouses throughout Europe. His recent book, Exceptional Treehouses, from which these images are taken, is an ode to these dreamy arboreal designs. Like a fairytale book for adults, every page features an image of a treetop perch to make you gasp. "People love treehouses because they are all about remembering childhood and childhood dreams," says Laurens, whose clients have ranged from businessmen to grandmothers. "They want their own special place," he says. "They want to be elsewhere, to be in their own world. It's an escape inside themselves." Treehouses have been enjoying a growth in popularity in the United States too, thanks largely to the work of designer/builder Pete Nelson, who runs Treehouse Workshop in Seattle and has written books on the topic. Nelson says he builds treehouses as "escape pods" for creative people who want a whimsical, out-of-the-ordinary retreat or studio space. "Usually, it's just a place to get away and meditate and leave behind the stress of the everyday," he says. "Often, it starts out as a child's treehouse and then the parents say 'forget the kids, let's have a studio here' and it becomes an adult space." The attraction of a treehouse, Nelson says, is that it puts you "directly into nature," but also speaks to something deeper within us. "It's been said that when you get up a tree your heart rate drops. I think it's a really primal thing. Our human ancestors climbed the trees to escape from predators, so naturally, we feel protected when we're up in the trees. "Treehouses hold a lot of sentimental value for people. They are a return to innocence. But I think there's something more primal going on too." Much of the lure of a treehouse, of course, is the idea of being elevated into the world of the treetops. There is something very humbling about just being in the presence of a big, venerable and ancient tree. For Laurens, one of the greatest joys is the chance to commune with the magnificent trees that have stood, tall and honest, since Napoleon's time. "It is a big emotion," he admits. "When you climb up into a treehouse in an old, old tree and you are the first person in the world to touch the trunk of that tree 14 metres up, it is like walking on the moon, it is so other-worldly." The treehouses built by Laurens' company are all constructed with sustainability and the welfare of the trees in mind. His carpenters use a special binding system and stilts to avoid driving any nails into the host trees. "We always like to be sweet with the trees. We don't use nails - never, ever," he says. "We respect the trees and we try not to disturb them. We don't cut any big limbs - we don't hurt them." Many of the designs feature spiral staircases that wrap around the trunks like outer springs. The designs are so organic, the trees look as if they have grown up through the winding stairs. Inside, these hideaways are reflections of their owners' dreams; some are dedicated to lounging, filled with cushions and day beds swathed in diaphanous mosquito netting. Others have more sophisticated fit-outs. "My favourites are the little ones that are very, very simple structures. They're the true treehouses," says Laurens. "But sometimes, for good reasons, people ask for more facilities." He retreats to his own treehouse - a simple structure built in an old pine in Luberon, Provence - whenever he can. "I go there to listen to music, to have a siesta and to read. "Being up in a treehouse, is like being in a different kingdom of the branches and the imagination."