Being ill, treatment at health centres causes anxiety and stress with children. This has a negative effect on their wellbeing, healing process and more important, their cognitive, motoric and social development. The goal of this thesis is to describe a set of generic properties for the built environment to reduce this negative effect by stimulating the imagination of children, aged 3 to 6 years. The generic properties are derived from the analyses of spatial elements, present during activities, in which the imagination is active: playing and perceiving art. Through play they develop their motoric, social and cognitive skills, including their imagination. In addition, not all children in healthcare institutions are able to play, therefore also perceiving art is studied. Through observations at different play areas and the (spatial) analyses of these areas, playgrounds (designed by Aldo van Eyck), fantasy worlds of children and different artworks a set of properties is determined; a place which stimulates the imagination must be created by the composition of different elements. In this composition their scale, number, variety and interrelationship are taken into account. Each of these elements can be described by their properties: height & planar differences, contrast, whether they can exists of loose materials, can be manipulated or that they support enclosure. The composition of these elements and the abstraction of their shape creates a framework of information. Certain aspects are visible and other aren’t. This results in the stimulation of the imagination. These results are translated into a design tool and forms the starting point for the design of a treatment and prevention centre for obese or overweight children. Obesity is a problem which has increased the past few years and probably will become bigger. This centre is located in Zuidwijk, Rotterdam. The percentage of children with obesity is higher in this area than in other parts of Rotterdam or The Netherlands. This centre exists of a treatment centre, sport centre and restaurant. The centre doesn’t only focus on the treatment of children, but also on the prevention and the promotion of a healthy life style of the children, their families and the neighbourhood