An innovative plant (10) for the production with the “spun bonding” technology or similar of a web (V) of non-woven fabric, comprising: a melting station (11) suitable for receiving and melting a polymeric base material (MR), an extrusion bar or head (12) with a plurality of extrusion or drawing nozzles (12a) adapted to receive from the melting station (11) the polymeric material (MR) in the molten state to produce a plurality or bundle of continuous filaments (FF); a conveyor belt (13) adapted to advance along a direction of advancement (A) and to receive from the above the continuous filaments (F), produced by the extrusion nozzles (12a), so as to form a web (V) of non-woven fabric; and consolidation means (14) designed to consolidate the non-woven web (V) formed on the conveyor belt (13); wherein the plant (10) is characterized by a special structure (20) comprising a base platform (21), rotatable (f, f′, f″) around a respective vertical rotation axis (X), and wherein the melting station (11), suitable for receiving and melting the base polymeric material (MR), and the extrusion bar (12), suitable for receiving from the melting station (11) the polymeric material (MR) in the molten state, are totally built and solidly supported by this rotatable base platform (21) (f, f, f), so as to be rigidly connected to each other without the interposition of any rotating joint. Advantageously, the plant (10) allows to vary, without interrupting its operation, the width (L, L′, L″) of the non-woven web (V) produced by the same plant, by rotating (f, f′, f″) and adjusting the base platform (21) around the respective vertical rotation axis (X), so as to vary the inclination (a) of the extrusion bar (12) with respect to the direction of advancement (A) the conveyor belt (13).