sentences:  Cow Tower is an artillery tower that was built in the city of Norwich, Norfolk, England, between 1398 and 1399.Norwich was a prosperous city in the late 14th century, with a population of around 5,000 involved in key medieval industries and forming a centre for international trade.Between 1297 and 1350 the city had erected a circuit of defensive stone walls and ditches, both to impress upon outsiders the status of Norwich as a great city, but also to defend against invasion or civil disorder.