Dasparkhotel is an experimental hotel in Austria which was converted into hotel rooms from drain pipes. Each room has – full headroom, double bed, storage, light, power, woolly blanket and light cotton sleeping bag. All other hostelry devices (Toilets, showers, minibar, cafe, etc) are supplied by the surrounding public space.
Costs are very flexible. They offer "pay as you wish" system where customers leave a Euro amount that they can afford and with which they wish to support the project.