Heaven is a spiritual domain where the most high God is. Although we have many Heavens according to our teacher, we have many Heavens.
So different spirit operate in different heavens and those spirits heave their duties and work, operating according to their heavens.
Now we have this heaven where God the most high is domicile here, there are certain angels that can't even get there let alone a human being. A highly consecrated place where only God and his son Jesus Christ and the 24 elders are.
No human has ever been there. Whether it is through trance or vision. No one has ever been there.