The Cambridgeshire Fens covers an area of about 200 square miles of very flat land, between the cities of Peterborough and Cambridge.
The land was originally very marshy with just a few areas of more solid ground where settlements were built. The suffix -ea- means island and consequently many of the place names end in 'ea' or 'ey' : Ely, Whittlesey, Manea, Thorney.
In the 17th century, the Fens began to be drained and much of the area today is still criss-crossed by a network of man-made rivers and dykes.
The history of the Fens is fascinating and if you would like to read more the website of the Great Fen Project is a very good place to start.