Dark and neglected 'that's the kind of derelict space that lurks below most highways and elevated roadways. Cities in the process of densifying, however, can no longer afford to ignore such concrete underbellies. Toronto, which has been busy completing 70,000 residential units between 2008 and 2012'mostly condominium apartments'recently opened Underpass Park, a gutsy template that repairs a previously marginalized urban zone in the city's East End neighborhood.