borough (district), administrative and historic county of Hertfordshire, England. The borough comprises the valley of the River Lea (a tributary of the Thames), which flows from north to south along its eastern boundary, together with the lines of road and railway that follow the west bank of the river and the ribbon of settlement that has grown up along these routes, from Cheshunt and Waltham Cross in the south to Broxbourne and Hoddesdon in the north. Broxbourne town is located 17 miles (26 km) north of central London, and the borough lies within the capital's commuter belt; however, west of the Lea valley, extensive areas of park and woodland can be found. The administrative centre is at Cheshunt. Area 20 square miles (52 square km). Pop. (2001) 87,056.