The milky turquoise of Lake Tekapo, in the Mackenzie basin of New Zealand's South Island, is not light but stone. Glaciers in the Southern Alps at its head grind bedrock into a powder fine enough to hang in the meltwater, and that rock flour throws the blue-green back at you. The lake sits in open tussock country, with the peaks standing at one end of it. On the shore is the Church of the Good Shepherd, a small chapel of rough local stone put up in 1935 and now the most photographed building in the country. Inside, behind the altar where the stained glass would be, there is a plain pane of clear glass with the lake and the mountains in it. Nothing was put in the way.
The same decision governs the nights. Since 1981 every town in the basin has been required to shield its outdoor lights and point them at the ground, a rule written to keep glare off the observatory on Mount John. What it bought is a sky you can read with no equipment at all. From the dark shore the Milky Way arcs from ridge to ridge, the Southern Cross and both Magellanic Clouds stand out plainly, and on a moonless night the galaxy is bright enough to show you the ground at your feet. If the water is still, all of it comes back doubled. On the hill above the town, guided tours open the University of Canterbury's research telescopes, the largest in New Zealand among them, and swing the domes onto Saturn's rings and star clusters the eye cannot reach. The one thing anyone did add here is the trouble. The lupins that flood the shoreline purple and pink in late spring were scattered along these roadsides in 1949, and they have since smothered the braided riverbeds where the wrybill and the black stilt nest. Everything else in the basin has been kept out of the way, and the galaxy still comes up over a lake with towns around it.