an old steel bike frame & rim once... The tree grew around it, and at some point years before the tree died, the frame was cut flush with the trunk & bark covered it up.
Never would have known or suspected it was there from the outside, as the bark was perfect & rough, but smooth( odd, but you know what I'm trying to say) Till I hit it and wrecked my chain...The homeowner showed me a picture of his firepit with the bike frame sticking out of a 25" dia log he was burning from that tree, spokes & all. I thought I hit fencing pipe at the time.