In 1917, while shells were still falling on the Western Front, the New Zealand government began planning for what would come after. Returning soldiers needed land, and the remote Mangapurua Valley - whose name translates to 'abundant stream' in te reo Maori - seemed to offer it. The valley sat deep in the interior of the North Island, accessible only by the Whanganui River and its paddle steamers. The government carved 35 holdings from the bush and offered them to veterans willing to break new ground.

For a time, it worked. Families arrived, felled trees, ran cattle. A school opened to serve the growing community. But the valley fought back. The terrain was steep, the soil thin, the rainfall relentless. Without proper roads, every transaction - selling livestock, buying supplies, getting children to school - required a journey by river. The isolation that had kept the valley empty for millennia proved equally effective against twentieth-century settlement.

Construction began in January 1935, by which time the valley's population had already collapsed. The Raetihi firm of Sandford and Brown built the bridge for the Public Works Department, hauling aggregate from the Rangitikei River and contending with floods and landslips that repeatedly stalled progress. When the work was finished in June 1936, the bridge spanned 130 feet across the deep Mangapurua Gorge - an impressive feat of concrete engineering, 125 feet above the stream. Labour alone cost 598 pounds, 11 shillings, and 7 pence; cartage of materials added another 419 pounds.

The bridge was meant to carry vehicular traffic to the Whanganui River, connecting the settlers to the riverboat service that was their lifeline. But by the time it opened, there were almost no settlers left to use it. Economic hardship and the sheer difficulty of access had driven family after family away.

By 1942, only three families remained in the Mangapurua Valley. Then came the January flood - a deluge that washed out what remained of the road network and forced the government to make a decision it had been avoiding. No further funds would be spent on road maintenance. In May 1942, the government officially closed the valley for settlement, just six years after completing the bridge that was supposed to open it up.

The bush began its reclamation immediately. Native trees pushed through abandoned fences. Vines wrapped around chimney stacks. The road that once connected the farms dissolved into the forest floor. Today, hikers who make the 45-minute walk from the Whanganui River to the bridge pass disappearing fence lines, stands of exotic trees planted by settler families, and the occasional brick chimney standing alone among the undergrowth - ghosts of domesticity in a landscape that has firmly reasserted its wildness.

Reaching the Bridge to Nowhere requires commitment. Most visitors travel up the Whanganui River by jet boat or canoe, then follow a maintained bush trail for 45 minutes through native forest. Mountain bikers can reach it via longer backcountry tracks. There is no quick way in, which is precisely the point - the bridge's power comes from its incongruity. You walk through dense bush, hearing nothing but birdsong and water, and then suddenly there it is: a full-scale concrete road bridge, engineered for traffic that never came, arching over a gorge in the middle of nowhere.

Heritage New Zealand has classified the bridge as a Category 1 historic place, and the surrounding Mangapurua Valley is a registered historic area. The bridge has become one of Whanganui National Park's most popular destinations - a destination reached, ironically, by the same difficult journey that defeated the settlers it was built to serve.