Secrets of the City – Gumbramorra Swamp Thing! was a collaborative project by Dennis Kratz and public artist Graham Chalcroft, designed to engage Marrickville residents in creating ephemeral public artworks and performances inspired by the historical footprint of the Gumbramorra Swamp. Over a month, the artists held free workshops where community members contributed their interpretations of the area's heritage, culture, and ecology. Native plants were incorporated into the artworks, and a living sculpture was planted as a lasting reminder of the project.

The artworks, along with storytelling events and performances, were showcased during the Art in the Park event at Mackey Park, Tempe, on March 13, 2005. This project, supported by Marrickville Council’s Local and National Artist in Residence program and the Arts Grant Scheme, offered a unique platform for the community to express their connection to the local landscape and its ecological and cultural history.