Cambridgeshire, county (1991 pop. 640,700), 1,313 sq mi (3,402 sq km), E central England. The county seat is Cambridge. The county is divided into five administrative districts: Cambridge, South Cambridgeshire, East Cambridgeshire, Huntingdonshire, and Fenland. Most of the area is alluvial fenland, rising to the low, chalky East Anglian Hills in the south, with the Gogmagog Hills near Cambridge the most conspicuous feature. The main rivers are the Ouse, with its tributaries, and the Nene. Efforts to reclaim the fens date back to the days of Roman occupation, but in the subsequent periods of invasion by Danes, Saxons, and Normans they were abandoned. The fens were drained after the Dutchman Cornelius Vermuyden completed a vast drainage project in 1653. Agriculture and light industry are the dominant economic activities. Wheat, barley, potatoes, sugar beets, and fruits are raised. Food processing is an important industry as well as radio engineering and the manufacture of cement, bricks, and scientific instruments. The town of Ely has been an ecclesiastical center for centuries. The Univ. of Cambridge dates from the 12th cent.