Ramakrishna Paramahamsa says (Gospel of Sri Ramakrishna, chapter 12, available here - http://www.belurmath.org/gospel/index.htm):
[Ramlal sings these lines]: Above, in the throat, is the sixteen-petalled lotus flower,...Transcending which, one sees at length the universe in Space dissolve,
the Master [Sri Ramakrishna] said to M.: "Listen. This is known as the vision of Satchidananda, the Formless Brahman. The Kundalini, rising above the Visuddha chakra, enables one to see everything as akasa."
Others have described it as seeing Brahman, but like having a pane of glass still between the soul and Brahman. It is called Aparokshanubhuti - Transcendent Perception. Actual merger occurs in the highest chakra.
How to get there - exterminate the senses. Swami Vivekananda says (Complete Works, V7, p 71)
Control the mind, cut off the senses, then you are a Yogi; after that all the rest will come...You continually do it unconsciously as when your mind is absorbed; so you can learn to do it consciously.
Notice - "...after that all the rest will come..." Learn to control the senses, then you can sit back and the 'wind of the grace of God' will unfurl your sail and take you to the goal. My guru used to say - what we want is freedom from the senses, not freedom of the senses. All the different practices have one goal in mind - control of the mind and freedom from the senses. There are different practices for different people.
How to exterminate the senses? Find your guru. All the scriptures tell you this. Your guru can look at your face and know what is your way.