Work begins on Europe's largest man-made nature reserve
17 September 2012 Last updated at 13:02 BST
Construction work has begun on Europe's largest man-made nature reserve, located in Essex.
Wallasea Island is being transformed from farmland into a 670-hectare (1,500-acre) wetland.
The site is using 4.5 million tonnes of earth excavated from the Crossrail project, for which a 21km (13 mile) tunnel is being bored through London.
The land will be transformed into marshes, lagoons and mudflats to attract birds and other wildlife.
The Royal Society for the Protection of Birds (RSPB) reserve is due to be completed by 2020, and will cost about £50m in total.
The BBC's Rebecca Morelle has been along to find out more.