Historical Christianity has never questioned the validity of heaven. In fact, the early confessions and councils all agreed on an eternal state, lasting for eternity for those counted among the redeemed of Christ Jesus. The exclusion of those not redeemed has never been questioned either. Albert Barnes states in his commentary on Psalm 95:11, “Unbelief shut them out; and this fact is properly made use of here, and in Heb. 3, as furnishing a solemn warning to all not to be unbelieving and rebellious, since the consequence of unbelief and rebellion must be to exclude us from the kingdom of heaven, the true place of “rest.”
First, the bible declares clearly and positively that there is an eternal rest for those who are in Christ Jesus. Jesus declared to Nicodemus in chapter 3 of the book of John “that whosoever believeth in him should not perish, but have eternal life. For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life. For God sent not his Son into the world to condemn the world; but that the world through him might be saved.” 
Again, 1 John 2:25 states, “And this is the promise that he hath promised us, even eternal life.”
John further declares in 1John 5:11 “And this is the record, that God hath given to us eternal life, and this life is in his Son.” And then concludes with the powerful verse in 1John 5:13 “These things have I written unto you that believe on the name of the Son of God; that ye may know that ye have eternal life, and that ye may believe on the name of the Son of God.”
So, without much argument, we can see by just a few scriptures that Jesus is the only way to access eternal life, but then comes another question; “Where will this ‘eternal life’ be spent? Will it be here on earth, or in heaven, or just some state of mind in never-never land?”
Again, historic Christianity finds itself in firm agreement with the Bible that heaven is not of this world. In fact, it is clearly of another world. Jesus was speaking in the treasury to a group of Jews who evidently misunderstood what he meant when he declared that he was not of this world; “Then said Jesus again unto them, I go my way, and ye shall seek me, and shall die in your sins: whither I go, ye cannot come. Then said the Jews, Will he kill himself? because he saith, Whither I go, ye cannot come. And he said unto them, Ye are from beneath; I am from above: ye are of this world; I am not of this world. I said therefore unto you, that ye shall die in your sins: for if ye believe not that I am he, ye shall die in your sins.”
Jesus plainly declared to Pilate on the eve of his death that his Kingdom was not of this world. 
So where is this Kingdom that Jesus spoke of?
There is a disconnect in our understanding of heaven in comparison to earth, because we have not experienced it even in the slightest form. We quip that something was “heaven on earth” when in truth we cannot compare the experience on earth with heaven because we have never tasted heaven. Hebrews 6:4 talks about “tasting” the heavenly gift, but not heaven itself.
Paul once commented in this way about a man, and it is debated if he were speaking of himself or another, but he states, “I knew a man in Christ above fourteen years ago, (whether in the body, I cannot tell; or whether out of the body, I cannot tell: God knoweth;) such an one caught up to the third heaven. And I knew such a man, (whether in the body, or out of the body, I cannot tell: God knoweth;) How that he was caught up into paradise, and heard unspeakable words, which it is not lawful for a man to utter.”
Here the third heaven or paradise is referenced. The location is clearly somewhere above this earth, in a realm separated possibly from time and space as we know it. Either way, a person cannot travel there with a space ship. It is a spiritual journey that is taken by the power of God himself.
Because there is such discontinuity between heaven and earth, we can only speak meaningfully about it through analogies. And when one reads the book of Revelation, where our clearest pictures of heaven are painted, we see a glimpse of what heaven is like.
But let us not forget what an analogy is! The author of the book of Revelation says heaven is like this or like that because he is attempting to give meaning to something “not of this world.” To get a meaningful reference point for something “eye hath not seen and ear hath not heard nor has entered into the heart of man” is challenging, and must be aided by inspiration of the Holy Ghost for us to come anywhere close.
Imagine for one moment that you had never seen an elephant, nor heard of one. But you recently discovered an ivory carving. Upon asking what it was, you discovered it was the tusk of a bull elephant. Now, having someone describe the elephant to you, can you imagine for a second how confusing it might be? So what does the person describing it to you do? He gives you something comparable to the elephant, so you can form at least some kind of image in your mind. But upon seeing an elephant for the first time after the description, you would stand amazed at the immensity and stature of such a noble creature! This is what all analogies in the bible do for us as we see heaven described.
Anytime we see symbols in the bible, they point beyond themselves to a deeper, better reality than themselves. Look at the description of Jesus himself in Hebrews 1:4, “…Being made so much better than the angels, as he hath by inheritance obtained a more excellent name than they.”
After describing the tabernacle and all the furnishings and sacrifices we are told those were only patterns of something better, “It was, therefore, necessary that the patterns of things in the heavens should be purified with these; but the heavenly things themselves with better sacrifices than these. For Christ is not entered into the holy places made with hands, which are the figures of the true; but into heaven itself, now to appear in the presence of God for us:” 
What do we get in eternal rest?
So we know there is eternal rest, better than the rest we get here, but there is more.
Secondly, we discover some things about heaven that ought to cause us to rejoice.
Have you ever been afraid of the dark, or rather that thing that was lurking in the dark? In heaven, there is no night there, and no need for the sun, moon or stars, because God is the light in heaven. 
Not only that, but all the things that cause us to have our hearts broken, and the emotions attached to those things will be wiped away! Notice what John wrote, Revelation 21:4-5 “And God shall wipe away all tears from their eyes; and there shall be no more death, neither sorrow, nor crying, neither shall there be any more pain: for the former things are passed away. And he that sat upon the throne said, Behold, I make all things new. And he said unto me, Write: for these words are true and faithful.”
We see a small child fall and cut their knee. They rush crying to their mother who kisses all the hurt and tears away. But tomorrow, another fall, another scrape, and the tears are back again. Not so for heaven! We rejoice in that our tears shall be wiped away once and for all.
What is heaven? Can we understand it?
Sometimes something makes more sense to us when we are told what that particular thing is not, rather than trying to describe what it is. We may not be told all the details of heaven because of our limited ability to fully understand things beyond our present sense of perception. Thus, all the descriptions are of things we are familiar with. Notice what we read of the physical aspects:
Rev 21:21 And the twelve gates were twelve pearls; every several gates was of one pearl: and the street of the city was pure gold, as it were transparent glass.
Rev 22:1 And he shewed me a pure river of water of life, clear as crystal, proceeding out of the throne of God and of the Lamb.
Rev 22:2 In the midst of the street of it, and on either side of the river, was there the tree of life, which bare twelve manners of fruits, and yielded her fruit every month: and the leaves of the tree were for the healing of the nations.
Entering into this great Kingdom is not done by our own merit, nor our own efforts. In fact, the entrance has been secured by Jesus Christ for us. Paul wrote to young Titus concerning how the love of God appeared to man and stated that it was “Not by works of righteousness which we have done, but according to his mercy he saved us, by the washing of regeneration, and renewing of the Holy Ghost; Which he shed on us abundantly through Jesus Christ our Saviour;”
The forerunner of the Messiah, John the Baptist declared in Matthew chapter 3, “Repent ye: for the kingdom of heaven is at hand.”
Jesus, following suit in the very next chapter “began to preach, and to say, Repent: for the kingdom of heaven is at hand.
The kingdom is now and in the future. We are saved by grace, through faith in the Lord Jesus Christ now, and for eternity.
J.I. Packer writes, “The kingdom is present in its beginnings though future in its fullness; in one sense it is here already, but in the richest sense it is still to come (Luke 11:20; 16:16; 17:21; 22:16, 18, 29-30).”