The Netherlands is a small country with limited space for further urban development. Further the number of inhabitants is still growing which means a further need for houses, roads and additional workspace. The combination of the above means a densification in the build up areas. Conventional solutions may take too much space; new alternatives including Underground Construction are necessary. Conventional Underground Construction is an option but expensive. Therefore innovation is sought, for new construction methods, cost reduction and reduction of risks. One of the challenges TOT is the quest for a shallow tunnel in the Holocene soil layers. Whether this is feasible will be the result of the project. The methodology applied is the organisation of Creative Workshops. A positive setting is created where one is asked not to criticize ideas, but to come up with solutions that would make unconventional ideas work. In this way creativity is triggered in its utmost way. Characteristic patterns are broken through, leading to out-of the box solutions. Based on the results conceptual ideas research are formulated. The First round of TOT will be finished halfway 2008. Planning is going on to organize a second round.