In the vicinity of the Wellington region the main axial range of the North Island descends from the higher levels of the Tararuas, at 3,000 to 5,000 ft, to appear as a block of greywacke whose summit lies at an altitude between 1,000 and 1,500 ft. The whole block is intensely and closely faulted, and the resulting relief is best envisaged by the layman as a series of smaller blocks, with relatively flat tops and steep sides, standing at different levels owing to the differential effect of the close faulting. Mt. Kaukau at 1,495 ft is a classic illustration of the flat summit surface, and so is Mana Island at 398 ft. Between the blocks run rivers and streams which are associated either with relatively broad open valleys, as in the Tawa-Porirua area, or with very deep valleys and gorges, as with the Kaiwharawhara Stream. Most of the valleys follow a general north-south alignment. Impressed upon this general north-south alignment and upon the intricate pattern of relief is an equally distinct north-east-south-west trend, created by the downwarping of the eastern part of the block and resulting in the formation of a fault-angle depression occupied by the excellent harbour of Port Nicholson in the south and by a narrow valley filled with the deposits of the Hutt River in the north. A conspicuous feature of the downwarping is the major fault line which appears as an escarpment to form the northern (locally termed western) boundary of the Hutt Valley.
It was not until the publication some years ago of an aerial photograph taken at 40,000 ft that many of the region's inhabitants became aware of the essential simplicity of the area's topography and pattern of settlement. The north-south trend was revealed most clearly by the line of settlements extending along a valley from Johnsonville in the south to Tawa, Linden, Porirua, and continuing on through Paremata, Plimmerton, and Pukerua Bay. Equally clear was the fault line slicing the block along a north-east-south-west trend with the manner in which the settlements of the Hutt Valley followed this line extending from Upper Hutt in the north-east to Trentham, Here-taunga, Taita, Lower Hutt, Petone and the foreshore of the harbour. A little to the south of Johnsonville the two trend lines intersect at Ngauranga, where the main north highway, Number 1, joins the Hutt Road, which links the capital with the cities and boroughs of the Hutt Valley.
The region possesses only two outlets through which all road and rail transport must flow – to the Manawatu via the Ngauranga Gorge and motorway, and through the rail tunnel (2·8 miles) between Ngauranga and Tawa – to the Wairarapa via the Rimutaka Hill road and the Rimutaka rail tunnel (5 ½ miles) between Mangaroa and Cross Creek. The constricted access imposes a number of transport problems, especially as Wellington, in addition to its other functions, acts as the port for inter-island traffic. In the event of a severe earthquake (in 1855 a 5 ft rise was recorded), the total disruption of major transport lines appears to be an inevitability.
The abrupt juxtaposition of hills, sea, and town produces a montage of extraordinary variety, and an environment that is never wholly urban, rural, or suburban. The strident mixture of seedy Victorian wooden residences, heavy commercial architecture, multi-storey glass and steel structures, industrial plants, warehouses, and wharves is broken and relieved by the expanse and colours of the harbour, or the backdrop of brooding deep-green hills. Fresh suburbs look out over hill country that is at once sweeping, massive, and gently warped, but in detail is sliced into deep narrow defiles above which the sky appears as a distant strip. The town dweller is never without a view of the hills or the sea, which alter their hues as the weather ceaselessly changes. Days of dazzling brilliance when the salt-laden air itself seems to sparkle in the sunlight are succeeded by oppressively grey sheets of nimbus, or softer days when the humid clouds seem to hang like smoke on the hillsides. From the hillsides the town itself is subjected to endless views and panoramas that from one spot include the whole sweep from the harbour entrance to the Tararuas (snow capped in winter), and from another offer a vignette reminiscent of the Mediterranean.