A hand-cranked recumbent. When I first saw it coming towards me, I thought it and the vertical bike behind it - and I say vertical because the recumbent was 100% horizontal - were one thing: either a trike or a bike with a two-wheel trailer. But it was a 'normal' bike following a machine whose rider was absolutely prone on his/her (couldn't tell!) back, as if in bed - with no pillow - and cranking with hands. Wow.