在剑桥以北有一大片洼地,共200多万亩,称为“剑桥北大洼’(Fens或Fenland),那里绝大部分地面低于海拔4—5米,有些地方还低于平均海平面。由于地势低洼、排水不良,在17世纪中叶以前,那里大部分地面长期积水,有些地方虽然夏天露出地面而长 North of Cambridge has a large depression, a total of more than 200 acres, known as the "Cambridge North Dawa ’(Fens or Fenland), where most of the ground below 4-5 meters above sea level, in some places below average sea level due to Low-lying, poor drainage, before the mid-17th century, where most of the ground water for a long time, in some places although the summer exposed the ground long