Mount Arthur (Tuao Wharepapa in Māori) is in the Wharepapa / Arthur Range in the north western area of the South Island of New Zealand.

Mt Arthur is made of hard, crystalline marble, transformed (hardened) from limestone, originally laid down under the sea some 450 million years ago in the Ordovician.

Below ground are some of the deepest shafts and most intricate cave systems in the country, and exploration of these is far from finished.

[7] During the ice ages small glaciers carved smooth basins called 'cirques' high on Mt Arthur, polishing and scraping the tough marble.

The floors of the cirques are studded with sinkholes where surface water is taken underground into extensive cave systems.