> It took me a while to find it, but I can now tell you that the old railway tunnel in the Karangahake Gorge is 1.1 kilometres long. So that wasn't a bad estimate, considering you were probably jogging a lot slower than normal pace due to it being pitch dark with a slightly uneven floor.

Darn. I originally typed out "between a kilometer and a mile," but then I second guessed myself and figured it had to be closer to a mile after all.