According to someone familiar with this area... "These houses are called "Kolonihavehuse". They are small houses, about 30-40 m^2, with a garden. People who live in the city sometimes have these to have a little undisturbed garden somewhere. The houses usually have a living room, bathroom and a small kitchen. People do not actually live there, and people rarely sleep there. "
It may be seen as a complete waste of space, but at least it's a uniquely designed waste of space! You can see more images of the area via google maps here.
(via Clear Perspectives)