Complex sentence: Several cities also have plans to renovate some railroad infrastructure into parkland, including Philadelphia, St. Louis and Chicago, where the Bloomingdale Trail, a nearly three mile-long linear park on former railroad infrastructure, will run through several neighborhoods.
Split into simpler sentences: Several cities also have plans to renovate some railroad infrastructure into parkland, "including Chicago, Philadelphia, and St. Louis". In fact, Chicago is building the Bloomingdale Trail, which is a nearly three mile long linear park on former railroad infrastructure that will run through several neighborhoods.