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)))
"After the first glass, you see things as you wish they were. After the second, you see things as they are not. Finally, you see things as they really are, which is the most horrible thing in the world."
--Oscar Wilde on Absinthe