The seed-pods of these roadside Plane trees dangle in threads of two-or-more. When seen from a distance, with the naked eye, the effect is most disconcerting — as though one is seeing double.
Update for Jamie: I've added a closeup of one of the seed-pods. They have an inner diameter (minus the spiky bits) of about an inch, and the dark holes are where the seeds live, prior to dispersal.
Details: Nikon 18-70mm, 44mm, f/16, ISO 200.