Raurimu Spiral

The Raurimu Spiral (Māori: Te Koru o Raurimu) is one of New Zealand’s most celebrated railway engineering achievements.

 Located on the North Island Main Trunk (NIMT) line between Raurimu and National Park in the central North Island, it allows trains to climb or descend a steep 139-metre (456 ft) elevation change over challenging terrain.

Designed in 1898 by Public Works Department engineer Robert West Holmes, the spiral solved a major obstacle during NIMT construction.

A direct route would have required an impractically steep gradient of 1 in 24. Instead, Holmes devised a clever layout using the natural contours of the land: a horseshoe curve, three hairpin bends, two short tunnels (385 m and 96 m), and a full circle. Trains rise at a manageable 1 in 52 gradient, covering 6.8 km to gain the height while the straight-line distance is only about 2 km. Remarkably, the design requires no major viaducts.

Construction was labor-intensive but far cheaper than alternatives involving multiple large viaducts.

The spiral remains in daily use and has no viable modern replacement. It is recognised as an engineering masterpiece by the Institute of Professional Engineers of New Zealand and as a Category 1 historic place.

A viewing platform near Raurimu village offers excellent views of trains navigating the loops.⁠ 

This ingenious feat continues to showcase 19th-century railway engineering brilliance amid New Zealand’s rugged landscape.