Why should nature be more natural?

Henry David Thoreau, the 19th century American transcendentalist famously embarked on a two-year course in simple living when he moved to a small self-built cabin in a forest. Thoreau regarded this sojourn as a noble experiment with a threefold purpose. First, he was escaping the de-humanising effects of the Industrial Revolution by returning to an earlier, agrarian lifestyle. Second, he had more leisure and recreational time. Third, and most important, he was putting into practice the transcendentalist belief that one can best transcend normality and experience the Ideal, or the Divine, through nature. It's hardly surprising therefore that Thoreau quickly became an icon for everybody who wanted "to get in touch" or "commune with nature." But what is it about nature that makes it more "natural" than, say, a city? If by nature we mean the material world along with the forces and processes that produce and control all its phenomenon - the laws of nature as it were - then surely a city also qualifies since it doesn't fall outside any of these laws. If by nature we mean just the world of living things, then too cities qualify. No, it's actually a third definition of nature - namely, a primitive state of existence, untouched and uninfluenced by civilisation - that people like to apply when they mean nature to be somehow qualitatively "better" than a city. Unfortunately, this definition comes into being only because civilisation has come into being. Otherwise, there's absolutely nothing primitive about it. Or, if there is, then every cave dwelling ancestor of ours would have to be transcending normality and experiencing the Ideal, or the Divine, all the time. So would those diminishing pockets of humanity which have largely remained cut off from civilisation and even today live in Stone Age conditions. Humans make cities like corals make reefs. For their purpose, neither is more - or less - elegant or functional than the other. The amazingly intricate arbour the bower bird makes to attract a mate is not greater or smaller in creative architecture than the extraordinary complex circuitry built inside a microprocessor. Therefore, why should any Ideal or Divine choose to be rapped with, only in the ambience of one set of artefacts and not the other? Especially if it created both in the first place? Or is it simply we who wield the knife of discrimination and do the choosing on absolutely arbitrary grounds? How humanising is that?