It includes at least one platform defining a plane, first and second sets of complementary coupling elements associated with the tower section and the platform respectively, and arranged in levels. In a first relative position of the sets of coupling elements, the platform is allowed to pass, in a substantially horizontal position, through different levels of sets of coupling elements and in a second relative position of the sets of coupling elements, the platform rests with its second set of coupling elements on a first set of coupling elements of one given level. A device for moving the platform may be provided for fitting it inside the tower section. The first or the second set of coupling elements in different levels are aligned along a longitudinal direction inside the tower section.