orthumberland combines a coastal plain along the North Sea and an upland area of hills and moors inland. The Cheviot Hills extend along the border with Scotland in the north and form part of the Northumberland National Park, which is scattered with prehistoric remains. To the south, stand the remains of Hadrian's Wall, constructed by the Romans in the 2nd century ad to delineate the northernmost limits of the Empire. There are excellent walks along the wall, which stretches over 73 miles (117km) and passes through magnificent countryside.