Why does nick describe the valley of ashes as fantastic and grotesque in the great gatsby?

Nick thinks as the valley as fantastic because it is so different from what he has  seen of the upper class and  think of the valley as being better than their hollow lives. He also describes it as grotesque because it shows how "the other side" lives (Valley of Ashes shows the cons of industrial society and represents the suffering of the lower class)

The details that best show evidence of tribal traditions are, "never in the history of his people had a man married a woman who spoke a different tongue” and "it has never been heard," was the verdict of an old man speaking a few weeks later.