Background For many years, cities have grown without any environmental consideration. Urban areas often suffer from a lack of natural spaces and from the fragmentation of natural habitats. This can have a significant impact on air, soil and water quality as well as biodiversity. As ways are sought to address these problems, the use of natural areas in urban settings is becoming a key element in land development policy. The Chanteloup loop is located in the north-west of the departement of Yvelines in the Ile-de-France region. It is defined by a large U-shaped meander of the Seine which leaves an area of 2 384 ha of land surrounded on three sides by river. Most of the land in the ‘loop’ is uncultivated wasteland and has been identified for urbanisation. At present, several green areas are scattered around this territory with no connections between them. Objectives The 'SeineCityPark' project aims to demonstrate how the socio-economic development of an urbanised territory of 1 700 ha can be combined with the improvement of local environmental conditions through the creation of green urban infrastructure. It hopes to be the first step of an ambitious programme of sustainable economic development in the area known as the Chanteloup loop, approved by the French label "Eco-quartier" rewarding sustainable development of urban areas. The project will develop a management plan that will define a basis for sustainable socio-economic development of the Chanteloup loop. It will seek to rehabilitate a neglected quarry and restore it as green open space by creating an ecological and recreational park of 113 ha called Bords de Seine Park. It will create an active 1.4 km strip where an ecological transition will be implemented between park and city. The project will develop ecological infrastructure to link the Park to the Seine in the south and the rest of the green network in the north - the Hautil Massif. This aims to allow the free movement of land animals, birds, insects, amphibians and dragonflies across the urbanised territory. It will use natural clean-up techniques to tackle water and soil pollution and remove invasive aquatic and terrestrial plant species, including Japanese knotweed (Fallopia japonica), the black locust tree (Robinia pseudoacacia) and species of the genus Ludwigia. The works also aim to deliver a consistent ecological infrastructure which will play a key role in adapting to climate change, including flood control in the Chanteloup loop. Works will include the reshaping of 250 m of alluvial shore and the creation of 30 km of paths and 800 m of pier to manage human access. Finally, the project will seek to raise local public awareness on environmental issues to maximise the integration and success of the urban green infrastructure. Expected results: A development and management plan for the Chanteloup loop; Stabilisation of water and soil pollution in the Bords de Seine Park - with a significant decrease in pollution within five years of the project end; At least a 70% decline in the presence of Ludwigia and a 10-30% decrease in Japanese knotweed or black locust in the park - with full eradication within five years of the project end; Development of new habitats and species, especially aquatic species, in the park and increased biodiversity in urban sections; Increased mobility of insect and and amphibian species from the south of the loop (Seine) to the north (Hautil Massif), via transitional areas connecting green zones; and The project will also provide a good practice example of green urban development.