| Site of Special Scientific Interest | |
 Fleam Dyke with overgrown ditch to right (west) | |
| Location | Cambridgeshire |
|---|---|
| Grid reference | TL 551 539[1] |
| Interest | Biological |
| Area | 7.8 hectares[1] |
| Notification | 1984[1] |
| Location map | Magic Map |
Fleam Dyke is a linear earthwork between Fulbourn and Balsham in Cambridgeshire, initiated some time between AD 330 and AD 510. It is three miles long and seven metres high from ditch to bank, and its ditch faces westwards, implying invading Saxons as its architects. Later, it formed a boundary of the Anglo-Saxon administrative division of Flendish Hundred. At a prominent point, the earthwork runs beside Mutlow Hill, crowned by a 4000-year-old Bronze Age burial mound.