Long-distance footpaths and cycleways will snake through the Great Fen, including a north-south route between Peterborough and Huntingdon.
A mosaic of fen and open-water habitats, with reed beds, woods, grassland and lakes, will offer shelter for otters, bittern, dragonflies and other rare species.
Project manager Kate Carver said: "This is a hugely ambitious plan to recreate a large natural fen landscape within inland Britain.
"This secret corner of the fens will be restored over time as a place of natural beauty where birds, plants and animals can flourish and people can relax and have fun."
LDA Design senior partner Professor Robert Tregay said: "We aim to restore rich fenland with a sustainable landscape to counteract the effects of climate change."
The client, the Great Fen partnership, includes the Environment Agency, Huntingdonshire District Council, Natural England and several county Wildlife Trusts.