The First and Last by
mclachland.
For all there is magic in the world, there is also math. There is something beautiful, symmetrical, about a tree. It's ostentatious, sometimes almost dull in its simplicity, but its angles and sloping lines are perfect math, all numbers and cosines that leave him dizzy with humility. Sometimes he sits, even when Gaius is in the castle waiting for the herbs he'd sent Merlin to pick hours before, and just stares, memorizes, because he's the only one who appreciates it, who will remember it when it's torn down to make way for something new. Everything's always torn down for something new.
Merlin/Arthur and, well, trees. ♥
Also
This takes the WTF? award for this Sunday I think. Totally NSFW considering the first video has giant paper penises in it.