Raurimu Spiral

South of Taumarunui, the terrain is steep, but not unmanageable, with the exception of the stretch between Raurimu and National Park, where the land rises too steeply for a direct rail route.

The area was thoroughly surveyed during the 1880s in an attempt to find a route with a lesser grade, but the only viable possibility seemed to require a 20-kilometre (12 mi) detour and nine massive viaducts.

Though costly and labour-intensive, the scheme was still cheaper than the previous plan by Browne and Turner which required 9 viaducts down the Piopiotea River.

From the north, trains pass Raurimu station before going round a 200° bend to the left in a horseshoe curve, climbing above the track on which they have just travelled.

Trains then complete a full circle, crossing over the Lower Spiral Tunnel through which they have just passed which is 23-metre (75 ft) below, before continuing towards Wellington.