Administrative (pop., 2001: 552,655), geographic, and historic county, eastern England.
Greatly enlarged in the government reorganization in 1974, Cambridgeshire now includes part of the former county of Huntingdonshire and the Isle of Ely; the county seat is Cambridge . Prehistoric tracks ring the fens; drainage was begun by the Romans. Major structures include Ely Cathedral and the buildings of the University of Cambridge . Cambridgeshire is crossed by two major rivers, the Nen and the Ouse , with its tributary the Cam.