The Thurrock Thameside Nature Park at Mucking, on the north bank of the Thames Estuary east of London, was officially opened on Saturday by veteran wildlife broadcaster Sir David Attenborough.
Essex Wildlife Trust has restored the site to grasslands, woodland, ponds and reedbeds, attracting rare and threatened species including the skylark, adders, the shrill carder bee and water voles.
The Wildlife Trusts -- an organisation representing 47 local wildlife groups across Britain -- said the reserve will eventually expand to cover 845 acres, around twice the size of London's Regent's Park.
The wildlife haven sits on top of a 'pie-crust' up to 30 metres deep which covers the landfill site, The Wildlife Trusts said.
A visitor centre has been built on top of the former landfill, with hydraulic jacks installed to cope with settlement of the rubbish below the building, and the park provides a network of paths, bridleways and cycle routes.
"This is the beginning of a new chapter in the history of this part of the Thames Estuary," said Attenborough, President Emeritus of The Wildlife Trusts.
"The area has had its ups and downs. This wonderful nature area and the extraordinary new centre stand where there were once 230 Saxon dwellings - but in-between times the waste of six London boroughs has been brought here."
"We live in a crowded country and we need to respect its limits to sustain us. Positive change like this must become the norm ? and The Wildlife Trusts across the UK are trying to make that happen."
Peter Gerstrom, chief executive of Cory Environmental which owns the landfill site, said rubbish from London is still being transported from the capital by boat along the Thames but is now being processed in an energy-from-waste site which produces enough power for 100,000 homes.