A self-levelling system comprising a base (10) fixed onto a first external load-bearing structure subjected to natural stressing forces, a second internal flat structure (21) which is to be self-levelled, and a movable fixing system between said first and second structure. Said movable fixing system comprises a cylindrical element (13) slidable vertically along a base guide (11) on the basis of a first command, and fixed at one end to said base and at its other end to a ball joint (20), said ball joint being fixed to said second structure, a first actuator (24) associated between said cylindrical element (13) and said second structure (21), said first actuator (24) being operated on the basis of a second command, a second actuator (25) associated between said cylindrical element (13) and said second structure (21), said second actuator being operated on the basis of a third command, said first actuator being associated with said second structure at a first point, said second actuator being associated with said second structure at a second point, said first point being positioned on a first axis and said second point being positioned on a second axis, said first axis and said second axis being mutually perpendicular.