The optical storage medium comprises a substrate layer, a data layer, and a nonlinear layer with a super-resolution structure disposed on the data layer, wherein pits and lands having a size above a diffraction limit of a pickup for reading of the data establish a first and a second level of the data layer, and pits and lands having a size below the diffraction limit of the pickup are arranged on a further level of the data layer. In a preferred embodiment, pits having a size below the diffraction limit are arranged on a third level and lands having a size below the diffraction limit are arranged on a fourth level of the data layer. The optical storage medium is in particular a read-only optical disc comprising a phase-change material, for example AgInSbTe, for providing the super-resolution effect.