Milan’s metropolitan region is affected by severe flooding during heavy rain events because of the high sealing rate of urban areas and increasing effects of climate change. Among several measures planned by the regional government there is a wide retention area that has been planned as flood control device, which also creates high quality natural areas and reconnects slow-mobility routes and recreational spaces inside the Lura Valley park. The project consists of the implementation of two rolling basins connected by an open air ditch and a pond filled with ground water. The basins will be temporarely flooded by Lura river during intense rainy periods through natural inlet from the river bed, whilst the pond will recharge constantly the ditch to maintain wetland vegetation all over the year to guarantee its phytodepuration functions. The balance of ground movements within the project is null as the volumes excavated are reused to create mounds and dikes. Wide areas of the river banks and plains have been upgraded through afforestation with native species. The objective of the intervention is to renature and stabilize river banks through live staking and vegetated dikes, riparian afforestation, phytodepuration basins, zero-energy flood retention system (no pumping needed).