Mên-an-Tol is a small set of neolithic standing stones in Cornwall. Legend suggests it has a piskie (Cornish faerie) guardian that performs miraculous cures. When an evil changeling baby was passed through the stone hole it transformed back into a real child.
Alexandra Palace Playground, North London
Urban legend states that when a child is passed through Mên-an-Tol's modernist North London cousin, it emerges as a knife-wielding hoodie.