Car Dyke is a vast canal approximately 85 miles long stretching from the River Witham south of Lincoln to Waterbeach near Cambridge. There is a huge amount of uncertainty about when the canal was built, or its use, but it was present in the Roman period.
The canal follows the western edge of the fenland, hugging the 6m level, which was also thought to be the edge of the Iron Age coastline. The two main theories regarding the canal are that it was used for transportation, or for drainage. There is some suggestion that it was in place in the Iron Age, but there is little to support this theory. An alternative theory is that it marks a boundary line between large Roman Imperial estates to the west of the fen edge and Boudiccan tribes in the east. This idea would date the structure to as early as 60AD.
Car Dyke is still extant in several places in and near Peterborough. Frank Perkins Parkway follows the line of Car Dyke for several miles before it gets to Eye, where it turns sharply to the west and continues along the edge of Paston, Gunthorpe and Werrington until it reaches Peakirk. From Peakirk much of the canal is only discernible using crop marks, regaining its structure again in Lincolnshire. Much of the visible structure is scheduled, but can be walked along. Some of it exists within private property and cannot be accessed.