Great photo stream, the best tunnel I have been in is, "The Maze, Melbourne".
Some pictures I see of other tunnels around the place kick the shit right out of it (The Maze that is).
Wouldn't mind checking out that ACT drain some day.
oh yes yes, came in my pants in dreadnaught. how pretty, and sisters light painting came up a treat too!
i think my favourite in terms of history would still be maze tho, so many stories.
fortress in sydeny was nice too, nothing can describe the sound of the waves from 50m away on approach