One of my favourite talks of the AIGA Gain conference so far was Robert Hammond talking about the High Line. We've seen and heard all about the project, and know how great it is, but one interesting point he raised was that in order to sell the concept of the High Line, he simply needed to show photographs by Joel Sternfeld of the space. No design concepts were presented up-front, instead they relied on their audience to imagine the potential of the space instead.
He argues that if you show design concepts from the outset, people have expectations of the final output which ultimately would not have led to the creative development that proceeded.
Incidentally, I hadn't realised there was an entire programme of events that take place in and around the park.