Abstract: A floor for a cultivation area such as a greenhouse. An accommodating hole is excavated in the ground and a flexible holder for liquid such as water is placed therein. The top of said holder is provided with a supporting plate. By varying the level of the supporting plate, the level of the greenhouse floor is varied. The water can contain heat. Optionally there can be a further holder which, for example, contains liquid with different properties, such as a different temperature. A number of such holders can be incorporated in a greenhouse floor.