 The Middle Level Navigations are a network of waterways in England , primarily used for land drainage , which lie in The Fens between the Rivers Nene and Great Ouse , and between the cities of Peterborough and Cambridge . Most of the area through which they run is at or below sea level , and attempts to protect it from inundation have been made since the 12th century. nobody knows what the waterways looked like in the past , but it is thought that they were much larger than they are now.
The network was first recorded in the 12th century , when the rivers Nene and Great Ouse were joined by a natural channel