In the book, 'Through the Looking Glass' by Lewis Carroll, Alice ponders what the world is like on the other side of a mirror. Climbing onto the fireplace mantel, she pokes at the mirror and discovers, to her surprise, that she is able to step through. 

Imagine gazing at a window, only to examine the glass.  When we gaze at a window, we look through it to see what is beyond.  Looking through the glass reveals God's creation.  This is what Paul is referring to when he says that which is known about God is evident in his creation.  He further explains, 'for the invisible things of him from the creation of the world are clearly seen, being understood. by the things that are made, even his eternal power and Godhead.' Romans 1: 20  

The wrath of God is revealed from heaven against all who refuse to see or who merely examine the glass and those who suppress the revelation of God for vain imaginings and futile speculations. 'For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men who hold the truth in unrighteousness; because that which is known about God is manifest in them; for God hath shewed it unto them.' Romans 1: 18-19

The unbelieving suppress or exchange it for a lie. Instead of worshiping the Creator they make God a creature of their own creation. Paul explains that, 'Professing themselves to be wise, they became fools, And changed the glory of the uncorruptible God into an  image made like to corruptible man.' Romans 1: 22-23  They distort his eternal power and Godhead turning from Him.  

'For this cause God gave them up unto vile affections.' Romans 1: 26. 'And even as they did not like to retain God in their knowledge, God gave them over to a reprobate mind, to do those things which are not convenient.' Romans 3: 28  In the closing verses, Paul provides a description of evil. In this day, the world at large still approves of the practice of these sins.