Q. What does the following line mean?
So blot their maps with slums as big as doom."
 

The civilized world is the world of education, rich, prosperity, flowers, bells and domes. So these powerful people draw their own map. The dirty slums and scramped holes find no place in them. These are like little hells. The rich do not want to blot their hands with little slums like that of Tyrol Valley.