Deep in a valley in the New Zealand wilderness, clear cold water rushes across moss-covered rocks.
In the morning the mist rises up and lays across the valley. In the afternoon sun glints on the Pearse River, shafts of light filter through native tree canopy. It is a fecund, primeval place. The water has flowed down through tunnels in Mount Arthur, in South Island’s north-west, to meet at the Pearse Resurgence at its base. On the surface it looks innocuous, a calm pond. But beneath it is one of the largest and deepest cave networks in the world; unfathomable, an unknown habitat, seemingly bottomless.
