Heaven is a topic that is often misunderstood. In Heaven we're not going to sit on puffy clouds and play the harp all the time. We're not going to stand around and sing the whole time. Revelation 21 gives us a glimpse into eternity.
When the term "Heaven" is used in the Bible, it could mean one of three things.
Heaven
1.) The atmosphere
2.) Outer space
3.) "God's Headquarters"
It's pretty clear as to where the first two are, but where is "God's Headquarters"? Is it on another planet somewhere? No. No, it's not. It has been theorized that Heaven is in another dimension of reality. I'm not saying that this is true, just that it's a theory with some evidence. Physicists have concluded (somehow) that there are more dimensions than the four we know (i.e. length, width, depth, & time). It's interesting that there are some Biblical hints that may support this theory. When Jesus was baptized, the "Heavens were opened" (Matt. 3:16, Mark 1:10). When Elijah was taken from this world, he was "taken up by a whirlwind into Heaven" (2 Kings 2:12). When Stephen was stoned, he saw "the Heavens opened and the Son of Man standing at the right hand of God" (Acts 7:55).
God said that there would be a new Heaven and a new Earth. He said there would be no more tears of sorrow, no more death, and no more pain. How? "For [all] the former things have passed away; behold, all things have become new." Is that possible? Well, I imagine that if God made it once, He could do it again. Apparently, Heaven's going to be pretty engaging because Jesus said that He was going to prepare a place for us. "Puffy clouds and harps" doesn't really fit with "many mansions." God has a satisfaction guarantee on Heaven. If God says that Heaven is "very good," then I'd say it's going to be pretty awesome.
