The juxtaposition of the smooth man-made surface and the organic "natural" plateau is an intentional aesthetic feature. It's been part of eastern art for centuries and more recently western as well. I differentiate between the Scandinavian freehands, which aim to mimic nature, and the more recent ones that combine highly architectual/sculptural shapes and natural forms. There are pipes that are meant to look like you've picked it up from the forest floor and others that are undeniably shaped by a human but with "natural" portions left behind for interest. Both can be hard to achieve.
Picked up from the forest floor (Ben Wade):
Juxtaposition of human and natural (Pan Langjiang):
A bit of both (Kadesh Swanson):
![47062105_2497310267008891_5314522889175695360_n.jpg 47062105_2497310267008891_5314522889175695360_n.jpg](https://pipesmagazine.com/forums/data/attachments/233/233663-76f29b426928e1e847d8a943076ce486.jpg)