Thanks to the TreeTalk map of trees in London, I laearned that the maple across the road from my college halls of residence in 1996 is in fact an American Sweetgum. [via Ian Visits]
The map is obviously incomplete, but its existence hints at how London is made of trees thusly spaced. Greater London has almost as many trees as people and qualifies as a forest under UN rules, notwithstanding that a third of it is concrete.