Anybody with a nervous disposition should stop reading now – especially if they suffer from vertigo. One of those extraordinary projects which looks like a visualiser’s dream but which nobody thinks will ever be built is actually nearing completion. It is the Skywalk bridge – a glass-bottomed horseshoe with no visible means of support which will jut out over the Grand Canyon allowing visitors to look down 1,200m. Intended to form a source of tourist income for the Hualapai tribe, the bridge will open officially on 28 March. For architect Mark Johnson and the rest of the team, challenges include designing to resist high horizontal winds and magnitude 8 earthquakes. See construction shots here ; learn more here ; and see a video about the Skywalk here .