Seeing the Kingdom

If there's any one thing that Jesus spoke and taught about most during his public ministry, it was the kingdom of God/Heaven. Through numerous parables, comparisons, stories, and word-pictures, Jesus was constantly trying to hammer the reality and truth of the kingdom into people's heads and hearts.
So what is this kingdom Jesus was talking about? Is it a religious institution? Is it a collection of religious laws? Is it the church? Is it the whole of Christendom - all of our organizations, buildings, programs, activities, doctrines, record companies, magazines, and TV networks rolled up into one big lump? Is the kingdom merely those people who know and follow Christ? Is it something we as Christians are supposed to be building, a centuries-long construction project, or is it something that already exists, finished and complete?
In the Gospel of John's famous chapter three, Jesus had an interesting late night conversation with a man named Nicodemus, one of the religious leaders of the day. After Nicodemus tells Jesus that he believes He has come from God, Jesus replies that "unless one is born again, he cannot see the kingdom of God." When Nicodemus makes it clear that he doesn't understand what "born again" means, Jesus adds that "unless one is born of water and the Spirit, he cannot enter the kingdom of God."
Until recently, I always took that passage to mean that you don't get to go to heaven unless you get "saved" as modern evangelical Christianity defines it. While that may be essentially true, it doesn't seem to be the point that Jesus is trying to get across. Quite simply, He's saying that there is this thing called the kingdom of God that no-one can see or enter without first being born again - which implies that once someone has been born again, he or she can both see and enter this kingdom.
It's important to note that the verbs used for both "see" and "enter" are used in the present tense and do not refer to some future sweet by-and-by. Even more interesting, the verb used for "see" - the Greek work Eido - carries more meaning than just physically seeing something with the eyes. It also means to have knowledge of something gained through experience or to "see with the mind."
So then, is Jesus saying that by being born again of water and the Spirit - obeying Christ in baptism and actually receiving the indwelling of the Holy Spirit within us - we become capable of perceiving this kingdom (which was apparently already in existence when Jesus and Nicodemus were conversing), entering this kingdom, and gaining experiential knowledge of this kingdom? I'd say yes, that's what Jesus was saying.
So where is this kingdom, what does it look like, and what is it made of? Jesus states plainly when speaking to Pontius Pilate that His kingdom is not of (part of, located in, or originating from) this world or Kosmos, which denotes the sum total of the material universe and everyone living in it. Essentially, Jesus is saying that His kingdom exists beyond not only the political or religious systems of humankind, but outside (or other than) the entire physical universe as well. Scripture tells us that God is a spirit, and it would stand to reason that His kingdom exists in this spiritual dimension.
But what does it mean for us to perceive this spiritual kingdom, and how should that bear on what we do and say? I think Christ explained this in describing His own relationship to the Father? In several places in John's Gospel, Jesus indicates that He is not speaking or acting by His own initiative, but rather according to what He hears and sees the Father speaking and doing. Jesus was obviously able to perceive what was going on in the spiritual dimension - a capacity and a relational connection which the Father passed on to His followers through the gift of the Holy Spirit.
Could that be what the kingdom of God is all about - God doing, speaking, and moving in the spiritual realm, which is then mirrored in the physical realm by people perceiving this spiritual activity and following suit in their own lives?
Consider Christ's model prayer to the Father: "Your kingdom come, Your will be done on earth as it is in heaven." Does the kingdom really need to be any more complicated than this simple agreement between heaven and earth, God and man?
Here we come to what I believe to be the primary blunder of Christian history. Through gradual increments, we stopped seeing the kingdom as something God is doing and something which we need to perceive, enter, and submit our lives to, and we started viewing it as something we're supposed to build in God's honor through our own efforts. We started building temples for God to dwell in, we established organizational structures patterned on human government, and we started measuring the success of our endeavors by material, worldly standards. Eventually, most Christians came to view their own institutional creations as the kingdom of God on earth, and that way of thinking still persists in a big way today.
Unfortunately, we have largely lost the essential element of spiritual perception and the essential truth that the kingdom is something we can never build on our own steam and wisdom; we're just not qualified for that task.
Truth be told, we're not even qualified to assist God in building His kingdom. We're not called to be kingdom builders; we're called to be building materials (living stones) in God's building project - just check out II Corinthians, 2:18-22 and I Peter, 2:4-5. Another way of saying it is that we - our lives and our relationships - are being built together by God into a new kind of kingdom.
At best, we can only build earthly imitations of God's kingdom through human efforts, in the same way that the tabernacle built by Mosses was merely a physical symbol of something that already existed in the spiritual realm. But while the physical tabernacle served its purpose in that time frame, the need for it vanished when Christ opened the door for us to enter as priests under His high priesthood into the spiritual original (see Hebrews, chapters 9 & 10).
With all that said, I think we as the modern church need to look for ways to disengage from our own efforts to build earthly imitations of God's kingdom and rediscover how to perceive, live in and submit ourselves to what He is building and doing.