Under the large forecourt of Paleis Het Loo, the Bassecour, a gigantic underground extension is being built that will serve as a Grand Foyer. Additional exhibition space will also be created in the underground extension. This new extension is connected to the Palace by four underground extensions under the existing Palace. This will create extra space for temporary exhibitions and public facilities. The complete underground extension and foundation is a design and construct assignment, was carried out by Volker Staal en Funeringen and consists of the construction of various construction pits and foundations near, under and in the historic buildings. The cofferdam on the forecourt has several compartments, due to the height differences to be bridged. The indoor construction pits are all equipped with very limited working space and working height using specialist techniques, making this a challenging project requiring us to think out-of-the-box.