The Milford Road does not so much climb as march into a wall. Past the beech forest of the Eglinton Valley and the long flat tussock of the Hollyford headwaters, the Darran Mountains rise in grey granite slabs on every side, and at the top of it all sits the Homer Tunnel, a rough, unlit hole in the rock that was a work-relief project for decades before it finally opened in 1953. It is just over a kilometre long and drops steeply toward the western end, and riding through it is a small adventure: cold, wet, loud, and more atmospheric than any modern tunnel has a right to be. The high section where the road approaches it is among the most dramatic stretches of tarmac in the country.
Everything here is about scale. Waterfalls hang off cliffs after rain, hundreds of metres of them, and in the right weather the whole valley is white with cascades. Kea, the cheeky alpine parrots, loiter around the tunnel entrance waiting for tourists, and they will happily unpick a seat or a bag strap if you leave your bike alone, so watch your kit. The Cleddau valley beyond the tunnel falls away in a series of hairpin bends, steep and tightening, down to the beech forest and eventually to Milford Sound itself.
This is not a road for hurry. In winter and spring it is closed regularly by avalanche control, and chains can be mandatory when snow is on the road, so check the local road status before you leave Te Anau. Summer brings tour buses and campervans, and the road is narrow in places. The best hours are early in the morning, when the light is low and the traffic has not yet arrived, or on the way back in the late afternoon.
Bring layers whatever the forecast says, since weather in the Fiordland mountains changes in minutes. And bring insect repellent for the sandflies at the bottom, which will take a tax on every bit of exposed skin when you stop.