"Then I saw a new heaven and a new earth..."
[See Ezekiel 40-48, which provides a background for this passage, though it is pretty long]
Many commentators have simply assumed that the "new heaven and the new earth" referred to in John's apocalypse is a description of the state of the world after the second coming of Christ. I'm not convinced that this is the only meaning of the passage. The language of a "new heaven and earth" is clearly borrowed from Isaiah 65-66, which is referring to a new social order - one in which all nations will worship the God of Israel, but where death will still exist. So it can't simply be a depiction of the eternal state. Rather, it seems to me that the passage is also about the church age prior to the consummation.