For your reference, Romans 1:20 (from the Message):
But the basic reality of God is plain enough. Open your eyes and there it is! By taking a long and thoughtful look at what God has created, people have always been able to see what their eyes as such can’t see: eternal power, for instance, and the mystery of his divine being. So nobody has a good excuse.
The phrase “for the natural things speak of the invisible” comes from an old song by Kevin Prosch:
For the natural things speak of the invisible
Look around and see
Who could deny the wonder of His love