In a BMW 745Li, Kevin Doyle discovers that New Zealand's northern half is a wholly enchanting place

To reel in a whopper, even a god has to think big. Maui Tiki Tiki-a-Taranga, a Maori deity and sportfisherman of some renown, recognized the limited allure of a worm on a hook. So, in an act of divine innovation, he tied a hook made from the jawbone of an ancestor to his line, daubed it with blood from his own nose, and cast it deep into the sea. What he pulled up was enough to startle even a son of heaven: The Maori call it "the fish of Maui." To the rest of us, it's the North Island of New Zealand. From my prospect behind the wheel of the elegant and substantial BMW 745Li, it looks like the place probably hasn't changed much since that fish tale was first told.

Day One: Auckland to Coopers Beach, 210 miles
As my co-pilot and I charge north on the motorway out of Auckland, one thing is immediately clear: The 745 is a force to be reckoned with. Passing a string of Holdens, Subarus, and Toyotas with ease, we dub our car the All Black, in honor of New Zealand's brutal and beloved national rugby team. The sobriquet is inspired less by our Bimmer's color—a shiny jet—than by the fact that with its stalwart profile and aggressive passing power the 745 dominates this road as assuredly as the All Blacks rule the field.

Just 20 miles from the high-rises that line Auckland Harbour, the land turns to pine-studded pastures. Horses, oddly outfitted in protective white sheaths from ears to tail, laze in the early-spring sun of a November morning. It's Saturday, and State Highway 1 is a slow-moving stream of cars with boats in tow, as eager urbanites flee the city to open their summer homes, or "baches," in the Bay of Islands north of Auckland. Drivers poking along in the passing lane zip to the left as the gleaming chrome teeth of our grille threaten to take a nip off their backsides.

Not more than 40 miles from Auckland, the road shifts east toward the coast and then crests, running past Orewa Beach and the whitecaps of Whangaparaoa Bay. There's a street fair today, and merchants are lined up along the beach selling their wares to a crowd milling around in sunglasses and swimsuits. An American flag as big as a bedsheet hangs from one of the stalls, whipping a welcome in the gusting breeze beside the flags of New Zealand and Great Britain. But we've barely covered any ground, and so continue up the coast, watching surfers wipe out on their boards.

I was looking forward to some coastal splendor, but State Highway 1 has other plans for us. In a game of hide-and-seek, it runs for a few miles along the water's edge and then veers inland again. Ocean panoramas are replaced by dense fern-carpeted forest, where the naked trunks of nikau palms are crowned with spiky fronds.

The 745 is so powerful and obedient that it invites pushing the limits of these roads, but I've seen too many police cars lurking in the shadows to give in to the temptation. Easing up on the accelerator, I decide to play by the rules, and find myself behind a dump truck belching voluminous black clouds of exhaust in our direction. Remarkably, the 745 is outfitted with a sensor that sniffs out such indignities and automatically adjusts the car's air-circulation system to protect passengers from the stink. It doesn't, we later learn, detect the aroma of fields freshly spread with manure, but, hey, it's a start.