ians got to walk along a block, scale a ladder or staircase, cross the street, descend back to sidewalk level, and continue onward.
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Eventually, of course, they finished the streets and built sidewalks at street level that actually were roofs over the old sidewalks.  For some time, there were two levels to the district: street level and the underground.  This situation persisted for almost a decade after the project was finished.  What finally drove residents to abandon the underground was a rapidly