Lambton Harbour and
Wellington Harbour is an arm of Cook Strait, covering some 76 km², with a two-km wide entrance at its southern end between Pencarrow Head and Palmer Head on the tip of Miramar Peninsula. It has a maximum length of over 11 kilometres and a width of 9.25 kilometres. The harbour has an entrance over 1.6 kilometres wide from shore to shore and as it is surrounded by hills over 300 meters high, it provides sheltered anchorage in a region where wind velocities may exceed 160 k.p.h. The depth of water over the great bulk of the harbour exceeds 20 metres or 10 fathoms.
The harbour is of seismic origin, and a major earthquake fault lies along its western shore. At the northern end of the harbour lies the narrow triangular plain of the Hutt River, which largely follows the line of the earthquake fault to the north-east. The city of Lower Hutt is located on this plain.
The central city suburbs spread around the hills overlooking the west and south-west of Wellington Harbour and its two large bays: Lambton Harbour and Evans Bay. Lambton Harbour is surrounded by the reclaimed land of Wellington's central business district and contains the majority of the city's port facilities. Evans Bay is an inlet between Mt Victoria and the Miramar Peninsula that serves as a flight path to low-lying Wellington Airport. Another smaller but popular bay, for its beaches and Cafes is Oriental Bay.
To the east of the harbour lie several small bays, most of which are populated by small coastal communities. The largest of these suburban settlements is Eastbourne, directly to the east of the northern tip of the Miramar Peninsula.
Three small islands are located in the harbour. To the south, close to Eastbourne, is Makaro / Ward Island Further north, close to the centre of the harbour, is the larger Matiu / Somes Island, to the north of which is the tiny Mokopuna Island
The entrance to the harbour can be quite dangerous, especially since Cook Strait to the south is notoriously rough. Close to the harbour's entrance lies Barrett Reef, its rocks breaking the water's surface at low tide. It was here in 1968 that the inter-island passenger ferry Wahine grounded during a storm, with the loss of 51 lives.