If you change the physical conditions that you're observing, then things get even worse. A giant tree is much easier to do when gravity is lower (The book "The Integral Trees" has an interesting example of 100 km long "trees" that are perfectly plausible under a certain very specific set of circumstances). A cylinder of stone 5 miles high is quite plausible under certain circumstances, but it's extremely unstable. If there is any sort of continuous energy input by an external agent to maintain the implausible system (e.g. a canal), then that implausible system will exist and may (depending on the category of the agent) be quite natural. A beehive or beaver's dam are both highly complex and implausible "natural" things that exist due to such continuous action.