'Grey to Green' is a ground-breaking environmental and economic development strategy devised by Sheffield City Council in the UK in 2013. The innovative inner-city renewal scheme transformed 1.6 kilometers of road space into a linear green route for pedestrians, cyclists, and public transport. A sustainable urban drainage system lies at the heart of this scheme, which responded to three key issues: [1] the need to re-connect the Castlegate area, including the Law Courts and Victoria Quays, with the rest of the city centre; [2] the need to re-use a large amount of redundant highway; [3] the severe impact that the floods in June 2007 had on Castlegate and [4] development of the project in four phases of implementation, which allows learning by doing so that improvements can be made in the solutions by evaluating the first phases of the implementation. Even with the recent completion of phase 2 in 2021 and with 2 more phases yet to be completed, the schemehas already significantly impacted the area. From an economic perspective, the scheme has led to significant development. New office and residential developments have taken place in West Bar and Castlegate and there is an improved likelihood of new sites coming forward for development. Visitors, residents, and workers enjoy the new seating and the surrounding planting. Besides these economic benefits, the project has significantly increased biodiversity and improved surface water management in the area.