The Rimutaka train line is steep. I know, I cycled it with Green Jersey. At times reaching a 1 in 15 gradient, it's not easy for a big old train and carriages to keep chugging along without losing control - hence the fell railway mechanism. One of only three remaining in the world, the Fell locomotive was busy in 1875, and brought here to be lovingly restored. Seeing the breaks worn after only one session down the hill, the pulled and cogs, and the steel and timber, you get a sense of the ingenuity and engineering - and the bravery of hose travelling to the top of the trail, Siberia.