I was just discussing this passage with a friend; it's from G.K.Chesterton's book Orthodoxy.
Let us suppose we are confronted with a desperate thing—say Pimlico. If we think what is really best for Pimlico we shall find the thread of thought leads to the throne or the mystic and the arbitrary. It is not enough for a man to disapprove of Pimlico: in that case he will merely cut his throat or move to Chelsea. Nor, certainly, is it enough for a man to approve of Pimlico: for then it will remain Pimlico, which would be awful. The only way out of it seems to be for somebody to love Pimlico: to love it with a transcendental tie and without any earthly reason. If there arose a man who loved Pimlico, then Pimlico would rise into ivory towers and golden pinnacles; Pimlico would attire herself as a woman does when she is loved. For decoration is not given to hide horrible things: but to decorate things already adorable. A mother does not give her child a blue bow because he is so ugly without it. A lover does not give a girl a necklace to hide her neck. If men loved Pimlico as mothers love children, arbitrarily, because it is THEIRS, Pimlico in a year or two might be fairer than Florence. Some readers will say that this is a mere fantasy. I answer that this is the actual history of mankind. This, as a fact, is how cities did grow great. Go back to the darkest roots of civilization and you will find them knotted round some sacred stone or encircling some sacred well. People first paid honour to a spot and afterwards gained glory for it. Men did not love Rome because she was great. She was great because they had loved her.