The dimension of Vaikuntha, the spiritual world is inconceivable, because in reality it is unlimited. The material world itself seems to us to have an unimaginable dimension knowing that what we perceive in this material cosmos is only part of the closed material universe in which we find ourselves and that it contains an inconceivable number of galaxies, all created by God on the same model as ours, “the Milky Way”. However compared to Vaikuntha, the material cosmos occupies only a quarter of the total creation of God, while the spiritual world occupies the other three quarters. The material cosmos which is the distorted reflection of the spiritual world is in reality akin to a cloud, which floats in the spiritual sky of all of God's creation.
No one can enter the spiritual world in order to serve the Lord at within its surroundings without being established in its pure spiritual identity, entirely free from all material stain.
In truth, an incarnate soul defiled by matter will transmigrate, will reincarnate into another body of matter because of its material consciousness, this is the “hardware”. Inhabited by material thoughts at the hour of her death, she was transferred by the Lord's assistants to another body of matter. In the same vein, when one establishes oneself in one's purely spiritual identity and meditates on the service of absolute love offered to the Supreme Lord, one is promoted to the spiritual realm to live there in the company of Krishna, God, the Supreme Person.
In other words, by thinking of Krishna and his companions in full awareness of his spiritual identity, one qualifies for access to the spiritual realm. No one can envision or contemplate the activities of the spiritual world without being established in his pure spiritual identity, and knowing in conscience to be a spiritual soul.
The Supreme Lord, Krishna says:
My sovereign home is a spiritual realm and absolute from which one does not return to this world of matter. Whoever attains supreme perfection, occupied in serving Me personally with devotion in this eternal abode, attains the highest perfection of human life and does not have to return any more to this world where there is suffering.
He is unmanifest and imperishable this supreme kingdom, ultimate goal, for which reaches it point of return. This world is My absolute abode.
It is only through devotional service, and only thus, that I can be known as I am. And the being who, through such devotion becomes fully aware of My Person, can then enter My absolute kingdom.