There were two thick and tall twin-trees, late in their nineties, black pines, rather closely side by side, which were available for a treehouse, seven metres up in the air, offering a view onto the city. The client wanted to give himself the special present of a treehouse for his 50 th birthday. The fact that the two trunks, up to a height of about ten metres, were more or less free of any branches, provided the perfect opportunity to realize my cherished dream of a spiral staircase surrounding the trunk. Initially, I simply envisioned to make use of only one of the pines for the staircase, from the end of which a hanging bridge would connect to the other trunk, at which the platform was supposed to be attached to. I, however, rather soon discarded this plan, as the distance between the two trunks was too small for this purpose. In spite thereof, I designed a construction, in which the spiral staircase leads directly through the platform, thus only one of the trunks being necessary. In March, when we were finally cleared by the building authority as well as the gardener, there was nothing left preventing the client from commissioning me, and rather soon we were able to get started. First, the steps and risers made from oak and larch wood were being prepared in my workshop studio, and subsequently these were attached to the trunk by means of steel brackets and robinia struts, at a distance of about ten centimetres to the trunk. We started with the uppermost step in order to ensure that the stair landing would be positioned exactly where we wanted it to be. In the next step, the railing made from robinia wine yard posts and a steel rope as a grab rail were being mounted. Upon completion of the terrace with about twenty square metres, and of the railing, we were in the position to start preparation works for a hut in my workshop studio. Using ropes, four people then lifted this hut up (in individual parts), which was then screwed together up in the air. The walls of the hut are composed of oiled matured timber, the blockstrip floor is made from larch wood, and the barrel-shaped roof consists of fragrant Swiss pine boards, covered by green panel sheets. The semicircular quarter light window made from steel that is mounted into the front, apart from two further windows, represents a central design element. A lot of love has been put into the restoration of the window, which was then being given two sashes by the locksmith. A sign indicating “Everything forbidden” decorates the little door at the front of the staircase, intended to discourage unauthorized persons. We expect the building to have only positive effects on the relationship between these two “elderly ladies”.