Road and canal building took place. Most famous road Ermine Street passes through western Cambridgeshire between Royston and Caxton Gibbet tp Godmanchester and Water Newton. Akeman Street connected Ermine Street to Cambridge, Ely and the fens. Wostead Street linked Godmanchester to Cambridge and Cambridge to the Colne Valley but was never completed beyond Horseheath. A spur connected the street to the camp at Great Chesterford, at the Icknield Way crossing. 'Way stations' built at Arrington Bridge and Horseheath.

Cambridge emerged as the provincial centre (Duropolis). Strategic site on dry land with river crossing and easily accessible.

A.D. 61 Castle Hill fortified in Cambridge, replaced a decade later with a stronger fortification. Cambridge grew from this fortification. Settlements established at Arbury, Barnwell, Newnham and Grantchester. By A.D. 200 this was the most populated part of upland Cambridgeshire and was acknowledged as the centre.

Fenland canals expanded, the greatest being Car Dyke best seen at Goose Hall, Landbeach. Commercial established proven by pottery unearthed at the harbour of Clayhithe near Waternbeach. Four canals built connecting the villages of Bottisham, Swaffham Bulbeck, Reach and Burwell. Reach Lode was a thriving trade route, Upware being a major port. Clunch quarries at Reach supplied stone for many fine buildings throughout the county.The 'Rodham Canal' was the straightening of the Great Ouse north of Littleport diverting drainage of the Fens from Wisbeach to King's Lynn. These canals opened the fenlands to settlement in the 2nd century A.D.

On the drier fen-edge between Cottenham and Fen Drayton and the then islands of March, Manea and Stonea, wheat was usually farmed elsewhere it was spelt or barley. The north of the county saw saltworks including a major development at Norwood Marsh. The centre of these enterprises was Stonea.

The claylands remained predominately forested except for major incursions at Comberton and Barton. Granta Valley was cleared of forest to make way for settlements at Linton, Bartlow and Horseheath. Villas existed at Icleton, Swaffham Prior, Bartlow, Comberton, Landwade, Girton, Litlington and Horningsea.

Roman security threatened by Saxons. British Coastal defences reorganised. A.D. 367 Saxons, Picts and Scots breached Hadrian's Wall and the Saxon Shore causing villas to be abandoned and the fortification of Cambridge by walls of limestone. Settlements across the Cam in the Round Church area were abandoned. Fen settlements declined due to flooding. Economic, military and political structure of Cambridgeshire fell into decay. Evacuation of troops A.D. 407 opened the province to invasion.