You have all wandered into the outer regions of darkness where it is very cold. Look at the answer to Lib's second question. This is man-made.
But we have a winner, and it's RAAK, with the Severn Tunnel. Your go.
Grows on a tree? (rather than a bush/on the ground etc)
Does it have a stone?
Canteloupe?
Clarification. Sorry to confuse you, I've confused myself too. so...
Fictional? (ie 1. the class of literature comprising works of imaginative narration, esp. in prose form. 2. works of this class, as novels or short stories: detective fiction. 3. something feigned, invented, or imagined. 4. the act of feigning, inventing, or imagining. 5. an imaginary thing or event, postulated for the purposes of argument or explanation.) NO
Fictitious? Having looked at many definitions, NO to most but YES to "imaginatively produced or set forth".
Sorry to get in a twist, hope this helps a little. (The dictionary definitions are to help my easily overwhelmed mind, as I know you are all far more eloquent than me!)