The Mohaka Viaduct is a railway viaduct spanning the Mohaka River in northern Hawke’s Bay, on the East Coast of the North Island of New Zealand, near the small settlement of Raupunga. It was built between 1930 and 1937 by the Public Works Department (PWD) for the New Zealand Railways Department (NZR). It is in length, and at , is the tallest viaduct in Australasia. Background Construction of the railway line from Palmerston North to Gisborne line began in 1872, connecting Palmerston North with Napier in 1891. The northern portion from Napier to Wairoa, and then to Gisborne followed much later, being built between 1912 and 1942. The section of line between Napier and Wairoa passed through difficult country, requiring heavy earthworks, five tunnels, five high steel viaducts to cross deep gorges, and numerous other bridges. Progress was slow, with portions of the line being progressively opened as sections were completed and handed over to the Railways Department. After completion of the line from Wairoa to the viaduct site in late 1930, the pre-fabricated steel work was railed from the small port of Waikokopu, about 40 km east of Wairoa. A start was made with the driving of test piles, and the digging of to deep foundations in the river bed, enabled by the use of pressurised caissons. The Government of the day faced major financial problems following the 1929 stock market crash in the US, and the onset of what would become the Great Depression of the 1930s. To cut costs work was suspended on most of the line, although foundation work continued at the Mohaka viaduct. Then on 3 February 1931 the Hawke’s Bay earthquake caused an enormous amount of damage to both the line and the associated works. Combined with ongoing financial difficulties, this caused the eventual abandonment of work all along the line, although the Mohaka viaduct foundations were finished before work stopped. The works lay idle until restarted in 1936, after a change in Government and some degree of recovery from the Depression. Preparatory work on completing the viaduct started in June 1936, and the completed viaduct was formally opened by the Minister of Public Works Bob Semple on 1 July 1937; it was nick-named "Bob Semple's Meccano set". It was built without accidents and ahead of schedule. When catastrophic floods in April 1938 washed away part of the low-level road bridge the viaduct was