I think it´s a feature - but I can´t bee 100% sure. The last time I was sat on it and took that shot was nearly 25 years ago. But it stil there because I saw it from below last summer. At least you didn´t ask how that guy with the one leg got there:o)))
"Got tight last night on absinthe and did knife tricks. Great success shooting the knife into the piano. The woodworms are so bad and eat hell out of all furniture that you can always claim the woodworms did it."