I happened to be checking my 2009 dairy and discovered - it was exactly six years ago today that I drove through an old mining tramway tunnel near Zeehan, Tasmania.
Zeehan is a mining town that had its boom years before World War 1. In 1910 the population was 10 times what it is now. The surviving buildings show evidence of the prosperity during that period, and are a somewhat peculiar style to American eyes.
Outside of town is an unpaved road to a historic mining area, with a one-way road through an old tramway tunnel. I believe the tramway was 24" gauge, while the main railway systems in Tasmania were 42" gauge. The tramway tunnel measures no more than 8 feet wide and 10 feet tall. I was concerned about driving my van through, but it was an adventure too good to pass up. Inside the tunnel you could see that numerous vehicles had scraped the rocky walls. If your vehicle stalled in there, you wouldn't have room to open a door.
My other railway highlight in Tasmania, a few days later, was a ride on the "Abt Wilderness Railway" from Queenstown. That railway was completely abandoned in 1963, but later reconstructed for tourist traffic and reopened in 2002.