It's an extraordinary piece of geography. As I fly into Nelson on a blue-sky day I see Boulder Bank. It's a long thin thread of grey stones, slicing the sea in two. On one side the sea is sapphire blue and corrugated by ocean breeze. On the Nelson side, it's green and smooth. The bank is an elegant arc with tighter curves at the south end towards Nelson city.
Nelson settlers chose obvious names. Boulder Bank, a 13km bank of boulders stretches from Glenduan southwest across Tasman Bay to the city and harbour. Nelson Haven, as its name implies, is a sheltered and safe haven tucked in behind the Boulder Bank. The safe harbour is the primary reason settlers chose this spot.
From a hill behind Nelson I see the Boulder Bank again; it hovers on the water in a surreal way. A lonely lighthouse is a mark of verticality, six cottages punctuate it at distant intervals and it ends with a big dot of an island. I want to go there.
It's a three- to four-hour stumbly walk over stones from its land end to the sea end so I take the easy way - a harbour and lighthouse cruise with Sailing Charters.
Skipper Martin Holmes explains that the New Zealand Company began the settlement of Nelson in 1842 and though Nelson Haven was a fine harbour, the narrow entrance made it difficult at night and ships regularly went aground.
In 1859 the Provincial Council approved plans for a permanent lighthouse on Boulder Bank. The 18m lighthouse was the second built in New Zealand. It was created in cast iron sections, by Stothert & Pitt, engineers of Bath, was shipped to Nelson aboard the Glenshee and the sections were all bolted together, on site. The oil-fired lamp was lit in August 1862.
Think about it. The decision was made, the money approved nearly 3000 the order was taken by sailing ship to England and the lighthouse designed and cast in Bath. It was shipped from Bristol to Nelson, built on the Boulder Bank and was operational all within thee years. It's a miracle of logistics and efficiency and wouldn't happen that quickly, these days.
When we land near the lighthouse, thousands of sea birds take flight; gulls, oyster catchers and terns squawk in protest. In the boulders at the base of the lighthouse hardy iris and foxgloves grow, remnants of the gardens left by the lighthouse keepers who lived here until 1915 when the light was converted to an automatic gas light.
We climb dark stairs in tight circles until we emerge at the top next to the complex and many-lensed light. Mirrors, magnification and magic meant that a tiny oil flame could be seen at sea for 12 nautical miles.
And on this clear day we see the mountains behind Nelson, the city clambering up and over its hills, a great stretch of Tahunanui Beach and far into Tasman Bay.
I peep, with my telephoto lens, down at the six lonely baches on the Boulder Bank. Generous distances separate them, as if neighbours are respectfully avoided.
I wonder who lives in them and why they chose this rocky edge when the Nelson area has oodles of pretty lakes and beautiful beaches.
I track down Kim Harris whose family have owned a bach on the bank for generations and he says his love for it is etched deeply into his being.
"The Boulder Bank has always been a part of my life, that of my parents and my children. My father's and brother's ashes are scattered there and my fondest memories come from the time spent there."
The Harris bach was built in 1889 as a fisherman's cottage.
"In those days fishermen needed to soak their hemp nets in pitch to make them last, so they boiled up the pitch then laid their nets along the boulders to dry.
"There was no space to spread nets in Nelson. They fished off the bank, too, and spent a lot of time out there."
Kim says his family go to the bach, "purely to relax, take stock and enjoy the simple things. We all fish and mess about in the boat.
"The harbour side is sandy and we play cricket and soccer at low tide and collect cockles.
"Beach combing, really an excuse for a walk, is a big thing for us; we gather wood for the fire. It's cosy in winter and we spend almost as much time there in winter as in summer.
"The bank is gradually moving and slowly getting higher.
"It lifted up half a metre over night during cyclone Bola and our old bach took on few more undulations but stayed standing.
"Storms are exciting. Spray hits the bach, the boulders tremble, the wind howls and seagulls squawk."
Kim says he sleeps well there, "the rhythmic rumble of rocks as they roll up and down with the waves and the sound of the sea" are a special kind of lullaby.
It takes about three hours to walk down boulder bank to the lighthouse from the road end at Glenduan. And it will take the same length of time to make the return journey by foot unless you have arranged for a boat to pick you up. Expect to see seals, dolphins and lots of seabirds.
Or take a boat, ph (03) 547 6666. sailingcharters.co.nz.
Liz Light stayed at Rutherford Hotel.