Time, redevelopment, and gentrification redraw neighborhood boundaries and erase what may have once been landmarks. They hide, bury, and obscure pieces of the city. They create layers in the built environment that are often invisible to passers-by, even to people who may have lived in the area for years.

There’s one Chicago group dedicated to rediscovering such lost moments in the city’s built and architectural history. The appropriately named Forgotten Chicago uses columns, photos, and online discussion boards to uncover and celebrate the obscure and the hidden: wood block alleys, disused fire stations, and “ghost signs,” those painted billboards on the sides of buildings that have faded almost beyond recognition.

They also conduct neighborhood tours that allow contributors to share their discoveries. These are not your out-of-town aunt’s architectural boat tour, although the group is planning an August encore to last year’s popular boat tour of industrial sites along the Calumet River. Forgotten Chicago’s tours explore things like pre-zoning Pilsen and Little Village, and remnants of the extension and removal of parts of West Ogden Avenue.

On Sunday the group staged a tour to explore underappreciated moments on Goose Island, an industrial zone in the middle of the Chicago River, and nearby Pulaski Park, once home to substantial numbers of Polish immigrants who worked in Goose Island’s factories. Co-founders Jacob Kaplan and Serhii Chrucky and contributor Dan Pogorzelski led participants through overgrown highway-side parks, urban renewal town squares, and what might be Goose Island’s oldest family owned manufacturing company. You can see some of their discoveries in the slideshow above, and check out future tours here.