The brain, spine and connection with the Soul, the Antahkarana, comprise the tower.
Along the spine are the Seven Major Chakras or parallel processors. As I said, these chakras rarely communicate. They rarely work together. The parable goes that because God was afraid that the Tower of Babel would be built so high as to reach heaven, he purposefully created different languages amongst the various people building the tower.
Because of the lack of communication the tower never got built to Heaven.
The lack of communication between the chakras, or the people building the Tower of Babel, symbolises their lack of integration. Because we are not integrated our psychic bodies will not reach up to heaven. We never managed to contact our Higher Selves. We are not Enlightened.
The Enlightened have built a Tower of communication "Twixt Heaven and Earth".
In the Ancient Sanskrit this Tower has been given the name "The Antahkarana".
It is the psychic wiring, created in mental matter. A thoughtform created dually by the Soul and the aspirant to connect the Crown Chakra through to the Soul and then to the spiritual triad and then the Monad.
Your evolution is the height of your Antahkarana.
The Astral plane is not flat. Although most people inhabit the psychic slums in the basement of the astral plane in their dreams, when they go to sleep.
It is the "Rainbow Bridge" whereby the Higher frequencies of the energy of the Soul are stepped down to that of the Earth, so that the Earth itself can raise its frequencies, can evolve. We have been created to help in this creative act.
These frequencies are stepped down Octave by Octave through each Chakra which are really Way Stations in the Energy System of the Soul. This is the "Music of the Spheres" of Pythagoras. Because The Enlightened Master Pythagoras was indeed talking of Chakras when talking about the Spheres or the Planets. Each Chakra as it evolves corresponds to one or more of the Planets. This is the secret of Astrology. This is the means whereby the Seven Sacred Suns and the Seven Sacred Constellations in this Sacred Universe affect us.
Each Chakra, when working correctly, acts like a Transformer in an Electrical system to halve the Energy Frequency of God. The frequency drops Chakra by Chakra, "Station by Station" as said David Bowie, on its way down to this planet because as Gurdjieff said "Normal Human Beings are transmitters of Cosmic Energy". And this is the function of Normal Human Beings. Those who are Enlightened. To transmit the Energy of The Soul. Whereby the higher energies of Truth, Prophesy, Intuition and Initiation are sent down towards this Planet.
Where the Higher Energy Frequencies of God create the Higher Energy Thoughtforms towards which the Median of the Masses are moved as they evolve and as the Earth Spirit Evolves.
Because the Energy Transmitted by the Enlightened is used to raise the frequency level of the Earth itself and all the people on it. To transmit the Light of Love down on to this planet of Love.
To dissolve the Selfishness of the separated selves, those "Law of the Jungle" Egos who cannot communicate with The Higher Self. Who think of themselves as Separate. Who think themselves Apart. Who do not know that they too are A Part of the Universe of God Itself. Those who are not connected. Those who have not been touched by God. Those who are not "Made".
The Enlightened exist to bring light into darkness. To dissolve the darkness and this itself is the meaning of the Sanskrit word "Guru". A person who dissolves or Transmutes Goo is a GooRoo.
And this is done through the Light of the Soul. Brighter than Ten Thousand Suns it exists alone. Unchangeable. Like Fire it lights everything with which it comes into contact. And once you are lit, you too burn with the Fire of the Soul. Like Prometheus you bring down the Fire of God onto the Earth, for the Benefit of every living being. Hari OM Tat Sat.