In the preparation and construction stages of the underground car park beneath Kruisplein with diaphragm walls, risk management played an important role. After a description of the structure and the construction, the preventive measures that were invented and carried out are summarised. These relate to the organisation of the project (experienced advisors, consequent risk management), the preparation of the construction stage (detailed plan of action, lessons learned from other projects, analysis of the environment and physical conditions), environment management, monitoring and the supervision of the construction process. The monitoring process and a new method to detect anomalies in the joints of diaphragm walls are presented in more detail.