Abstract: In order to provide versatile use for a surface that is provided with a covering of grass or the like, a plurality of bases are inserted in the subsoil of the surface below the grass covering for the support of a supporting structure that is provided with a floor covering that can be walked or driven upon. When the grass covering is used, the bases are covered by inserts that are adapted to be placed in the grass covering. When the surface is to be used for a different purpose, the supporting structure is supported on the bases in such a way as to be spaced from the grass covering. Illuminating means that are mounted on the supporting structure and that produce effects for photo-biological processes are provided for irradiating the grass covering, so that despite the covering, growth is not inhibited. Thus, the surface has a versatile use without having to worry about damage to the grass covering. Conversion is effected in a short period of time in an economical manner.

Abstract: An outdoor recreational area cover comprises a pylon support with a plurality of circular segment shaped cover members which have inner apices which are pivotally supported on the pylon support. All the supports are connected to the cover members at a spaced location from the pylon and they are arranged to roll over tracks or similar supports so that the cover members may be rotated around the pylon. By rotation, the cover members may be arranged so that they are foldable, one over the other, or extended fanlike to cover any desired recreational area such as a swimming pool. The segments are advantageously supported by generally vertical portions which extend downwardly from their outer ends and carry the rollers. The construction is such that the swimming pool or other area may advantageously be used when the cover members are arranged to overlie it.