In 1998 a study was conducted in the Netherlands into the possibilities of a more large-scale and systematic use of the underground in the western part of the country, the so-called 'Randstad'. It was intended to be a more focused sequel on a study conducted on the possible role that use of the underground could play for the whole of the Netherlands, the 'Strategic Study on the utilization of underground space'. The study examined the possibilities of improving an idealized model of the future spatial development of the Randstad, that was preferred by the provinces comprising this Randstad, by using more extensively he underground space. Improvement meant an enlargement of the efficiency of the use of space and maintenance or enlargement of the spatial quality of the area. Societal, cost, groundwater and policy aspects were investigated. The study showed some remarkable results. Gains in available space up to 50% in specific areas seemed possible and, when costs of working and maintenance were taken into account, underground construction for several facilities was no more expensive than above ground construction, which contradicts a widely held belief in the Netherlands.