A chill hangs in the van as you slip away from Christchurch, the city lights shrinking behind a ribbon of asphalt that crosses the flat, farming face of the Canterbury Plains. The road climbs; fields become hedgerows, hedgerows become tussock, and the air starts to carry the clean, mineral scent of stone and snow. By the time you crest Porters Pass—just under 1,000 meters and a higher saddle than Arthur's Pass itself—the Southern Alps are demanding your attention: serrated ridgelines, braided rivers working their way to the sea, and mountain lakes sitting like dark eyes in the valleys.