An indoor soilless plant cultivating system for emulating outdoor growing conditions, comprising: a) a plurality of stationary light posts (6a-h), each of which adapted to illuminate a predetermined sector of an indoor facility in accordance with a predetermined illumination signature; b) a plurality of plant growth towers (2a-c) that are exposable to the light generated at any given time by one or more of the light posts (6a-h) and that are arranged by at least one module defining a module darkened interior region within which instantaneously positioned plants receive a sensation of nighttime; c) a plurality of light elements mounted on each of said light posts (6a-h) wherein each of said light elements is provided with a directional lens configured to produce a light emitting angle whose angular boundaries are incident on a tower (2a-d) periphery, causing propagation of corresponding emitted light to said interior region of the module between two adjacent towers (2a-d) to be blocked as a result of its incidence on the tower (2a-d) periphery, to thereby ensure that said interior region will be darkened to a radiation level less than a predetermined photosynthetically active radiation level for the plant being cultivated; d) a drive unit configured to cyclically rotate each of said towers (2a-d) about a substantially vertical axis by a complete tower rotation once every 24-hour period so as to be sequentially exposed to morning light conditions, noon light conditions, afternoon light conditions and nighttime conditions in accordance with the illumination signature emitted by the light posts (6a-h) of the at least one module; and e) irrigation means for supplying the plants being cultivated in each of said towers (2a-d) with a nutrient-rich solution. a) a plurality of stationary light posts (6a-h), each of which adapted to illuminate a predetermined sector of an indoor facility in accordance with a predetermined illumination signature; b) a plurality of plant growth towers (2a-c) that are exposable to the light generated at any given time by one or more of the light posts (6a-h) and that are arranged by at least one module defining a module darkened interior region within which instantaneously positioned plants receive a sensation of nighttime; c) a plurality of light elements mounted on each of said light posts (6a-h) wherein each of said light elements is provided with a directional lens configured to produce a light emitting angle whose angular boundaries are incident on a tower (2a-d) periphery, causing propagation of corresponding emitted light to said interior region of the module between two adjacent towers (2a-d) to be blocked as a result of its incidence on the tower (2a-d) periphery, to thereby ensure that said interior region will be darkened to a radiation level less than a predetermined photosynthetically active radiation level for the plant being cultivated; d) a drive unit configured to cyclically rotate each of said towers (2a-d) about a substantially vertical axis by a complete tower rotation once every 24-hour period so as to be sequentially exposed to morning light conditions, noon light conditions, afternoon light conditions and nighttime conditions in accordance with the illumination signature emitted by the light posts (6a-h) of the at least one module; and e) irrigation means for supplying the plants being cultivated in each of said towers (2a-d) with a nutrient-rich solution.