Japanese designers Nendo have built an enormous woodland nesting box with 78 entrances for birds on one side and one big door for humans on the other (+ slideshow).
The treehouse was built for observing birds at the Momofuku Ando nature centre in Komoro, in Japan's Nagano Prefecture.
People can reach the Bird-apartment by climbing up a ladder and through a circular hole.
Spy holes across the back wall of the apartment allow a discreet view into the 78 bird boxes on the other side.
Other designs by Nendo we've featured include a tote bag with a pop-out hand puppet and a set of unstable furniture that has to be balanced by books and cups.