Artist Olivier Grossetête created a bridge suspended by 3 helium-filled balloons over a lake in Tatton's Japanese Guarden in the UK. Personally, I don't think I would try to walk it.
Grossetête’s artwork toys with the disciplines of design and engineering, with this particular piece an extension of his earlier 2007 work 'pont suspendu' - an installation along a similar vein of three large balloons supporting a bridge-like structure, hovering over château ferry lacombe in tret, France. The work evokes a sense of abstract delicacy, transferring fanciful imagery usually reserved for daydreaming to reality.
- More images at Design Boom
http://theweek.com/article/index/225856/is-the-world-running-out-of-helium