In the eco-district next to the water tower there is a small octagonal turret. In this Windketelgebouw (‘air chamber building’) there used to be a steel tank serving as an air valve. It contained water and air, and if a pump suddenly failed, an air lock would cushion the wave of pressure. Residents around the square bought this little building and turned it into a one-bedroom hotel. For € 300 you can stay two nights in this historic building, which has three floors and a fully furnished interior. It even contains a bath!