Posh Perches

Tree houses are generally thought of as rickety wooden hangouts for kids or the Swiss Family Robinson. But increasingly, adults are muscling in on the act, seeking not only quiet and solitude in nature's bosom, but creature comforts, too. The construction of wooden aeries is branching into new and bespoke areas: a number of European companies are offering solidly constructed, customized treetop retreats which, for prices from $15,000, may be designed to fit almost any species of tree.

While all arboreal dwellings are a treat for the senses—there's the smell of freshly cut timber, the creak of...