When Public Works Department engineer Robert Holmes designed the Raurimu spiral in 1898 he resolved one of the stickiest problems on the North Island’s main trunk line. Holmes was responsible for working out the exact route of the track. He had to find a way to get trains up a rise of 122 metres in 2 kilometres. The previous attempt to resolve the problem would have required nine viaducts and 20 kilometres of track. Holmes’s design used the topography to minimise the need to cut, fill and tunnel..It involved 11.3 kilometres of track and included two tunnels, three horseshoe curves and a complete circle. In 2005 the spiral was made a Category 1 Historic Place in recognition of its technological significance.