Raurimu Spiral

The Raurimu Spiral is a single-track railway spiral, starting with a horseshoe curve, overcoming a 139-metre (456 ft) height difference, in the central North Island of New Zealand, on the North Island Main Trunk Railway. It is a notable feat of civil engineering, having been called an 'engineering masterpiece'. The Institute of Professional Engineers (NZ) has designated the spiral as a significant Engineering heritage site.