Sycamore leaves are on the large side generally--about as big as my hand with fingers spread wide. But not this big. We had a strong wind for 24 hours or so starting sometime Friday, and on Saturday morning there were several of these freaks on the ground. They must grow only very high up on the tree, where they get most of the sun, because none that I can see from the ground are this big. I laid a coin (a quarter) on it just to give you some sense of the size: almost 18 inches/45cm across.