What is the terrible place Nick is referring to in the first line of Chapter Two of Fitzgerald's The Great Gatsby?

Chapter Two starts with a description of the Valley of Ashes, an area between West Egg and the heart of New York City.  This is a desolate area where the color grey is repeatedly mentioned.  This description adds to the gloom that overwhelms the area, and it is the first mention of the Eyes of Dr. T.J. Eckleburg, depicted on a billboard of a pair of glasses that look over the valley.  These eyes are an allusion to the eyes of God, who watches over the gloom, and sees what prosperity and enormous wealth can do to humanity.  Tom Buchanan's mistress also lives here with her husband, Wilson, who owns a garage and who will be central to the climax of the novel.  This chapter thus begins to introduce the reader to some of the complications the characters will deal with in the novel.