Dunas Pavilion.

The dunes south of the lagoon are protected habitat, home to rare thrift and nesting plovers. The municipality wanted a place to rest and shelter on the two-kilometre boardwalk without digging into the dunes.

We spent a spring walking the line with ecologists, and found the one hollow where a wall would sit below the dune crest, low enough to disappear from the beach.

The pavilion is a single white wall, forty metres long and 2.4 metres high, that turns its back to the north wind. Against its sheltered face, a pergola of pine beams on slender posts shades a broad bench and a gravel terrace planted with dune grasses.

The pergola's battens are spaced to cut midday sun by two thirds while letting the sea breeze pass straight through. In summer, lights are strung along its beams for evening walks with the reserve's guides.

The wall is built of lime-concrete blocks laid dry on a shallow timber raft, and finished in a white lime render renewed every few years. The pergola stands on twelve galvanised screw piles, driven by hand and removable in an afternoon.

Every joint is bolted, not glued. A two-page manual explains how to take the pavilion apart and in what order, should the dunes move or the municipality need it elsewhere.

The pine is untreated and has already turned silver in the salt air; the lime has softened to the colour of the sand at dusk. Marram grass is beginning to grow back along the foot of the wall.

That was always the plan: in ten years the pavilion should look as though the dunes put it there.