The River Plym, which flows off Dartmoor to the north-east, forms a smaller estuary to the east of the city called Cattewater. Plymouth Sound is protected from the sea by the Plymouth Breakwater, in use since 1814. In the Sound is Drake's Island which is seen from Plymouth Hoe, a flat public area on top of limestone cliffs. The Unitary Authority of Plymouth is 79.84 square kilometres (30.83 sq mi). The topography rises from sea level to a height, at Roborough, of about 509 feet (155 m) above Ordnance Datum (AOD). COUNT 5
QSN1 What estuary east of Plymouth is part of the River Plym? ANS1 Cattewater QSN2 When did the Plymouth Breakwater open? ANS2 1814 QSN3 What island is present in Plymouth Sound? ANS3 Drake's Island QSN4 How large is the Unitary Authority of Plymouth in square miles? ANS4 30.83 QSN5 In meters, what is the highest point in the Plymouth Unitary Authority? ANS5 155