Nebuchadnezzar is the tree that reaches to heaven. Already at an earlier time people in Babel tried to develop such a great power and culture that they wanted to prove that people are no less than God. As proof of their power, they wanted to build a tower that would reach into heaven. We read about this attempt in Genesis 11:1–9.
11 The tree grew and became strong, and its top reached to heaven, and it was visible to the end of the whole earth.