stream in England whose whole course of 50 miles (80 km) marks the boundary between the East Anglian counties of Norfolk and Suffolk. The river flows northeastward through agricultural countryside, and no major towns are located on its banks. Its lower reaches form part of The Broads, a network of inland waterways, and it reaches the North Sea through a channel at Lowestoft, but its mouth and that of the River Yare (Yare, River) is farther north at Great Yarmouth. Near the river's confluence with the River Yare, at the head of Breydon Water, stands Burgh Castle, of Roman origin.