A three dimensional folded structure, for use in lightweight design and lightweight construction, is folded at regular intervals and cannot be folded flat. The folded structure substantially extends in two directions and includes a small number of folded ply sheets. Each of the ply sheets is formed by an originally planar blank of an initially flat material lying in a zero plane and includes fold lines and polygonal holes disposed at regular distances. Each of the ply sheets is subdivided into a plurality of segments, each in the form of a polygonal planar entity that is, except at a border of the ply sheet, delimited by the fold lines and the border-edge-sections of a respective polygonal hole. Each ply sheet is folded up in two directions. During folding, the holes close into slits. Each slit of one ply-sheet is completely bridged by the other ply-sheet.