Generally speaking, there are other multiple correlations as well. In addition to the one with the three worlds in all traditional doctrines (higher, intermediate and lower), I can mention the three Hindu modes of material nature (Satva, Rajas, Tamas) and, paralleling them, the three individual types (Virtuous, Passionate, Ignorant) that can determine his or her destination in the after-life. Here too, by virtue of the strict analogical correspondence between macrocosm and microcosm, what is true of a world is also true of man.

If we depart now from the symbolism of three, there immediately come to mind the seven concentric rings that encircle Mount Meru, the Sacred Mountain of Hinduism and Buddhism which actually symbolizes the Pole or world axis.
 

This variation from three to seven enclosures is in no way arbitrary. The crux of all symbolism lies in the multiplicity of meanings it can convey, and the depth and usefulness of a particular symbol as a support in the teaching of the doctrine is directly associated to that multiplicity; in this sense, the particular variations it may present cannot but enrich such diversity and efficacy. For example, each of the above mentioned three worlds of the traditional doctrines are usually subdivided into three additional worlds, which makes them add to a total of seven (if the intermediate world remains as one) or nine (if it does not). What matters in this specific case is conveying the idea of a supreme center from which the doctrine radiates to the outer world or worlds, and the multiple analogies and correspondences of which such symbolic representation is susceptible can only be enhanced by such magnification. 

With these explanations, the meaning of the lines becomes all the more clear: they are certainly channels which communicate the traditional doctrine hierarchically, from top to bottom – i.e. from the supreme degree, which is that of its depository, down to the other levels. Now if the identity of top and center does not look very clear, one may imagine a cone from whose top the teaching radiates down to the circular perimeter at its base. The supreme  centre thus corresponds to the source of the teaching, the one Dante used to talk about, and which we can now parallel to Mount Meru, with the rings below and projecting outside corresponding to the world beyond and its myriads of creatures, and the cruciform pattern of four lines (which on the side of a cone actually would become indefinite) representing the four rivers of Paradise. 

With this said, there is still a difference, however, between the circular and square forms of the triple enclosure: while the circular form is connected with the symbolism of the earthly Paradise and therefore with the beginning of the present Manvantara or human cycle, the square form is rather associated with that of the Heavenly Jerusalem, which places it at its end. In effect, there is always a correlation between the beginning and the end of any cycle, and at the end of it, when final equilibrium is achieved, the circle is replaced by the square, which indicates the realization of that which the Hermetism symbolically refers to as squaring of the circle. In the first case, the supreme center is the source of the teaching and indeed of everything, i.e. God Himself; in the second, that center is not the source itself but the depository of the doctrine, a sort of priestly king who, as an envoy or delegate of the Highest Power, gives it to man and to the world at large.