In Philadelphia, the Reading Viaduct has been an urban ruin since it was decommissioned in the 1980s. Too massive to tear down, it has blighted an already downtrodden neighborhood. But that’s no longer acceptable. The blueprint has been drawn in New York: Build it and they will come. In fact, they’re already gathering. TheTrestle Inn has joined the pioneering Institute bar, and the new Underground Arts bar is on the way. With North Broad happening to the west and the Union Transfer music venue anchoring the South, Poplar’s time is coming, and the potential is great.