While I was hiking in Iceland last summer, I became quite sick and ended up going back to the city on my own a day earlier than I had planned for. My reward for this was the most exciting bus journey I have ever been on: through the numerous fjords in the Thorsmork area. This posting detailing a journey by some ex-American army vehicles through the same area will give you an idea of what my bus journey entailed:
In the first photograph, you can actually see the red-roofed mountain hut in the background which I camped beside.
Naturally to tackle those kinds of rivers, the bus I traveled on was a large 4x4 beast with a very high wheel base. The ticket for the journey was particularly expensive, apparently this was due to the insurance costs to cover the buses being so high.
I'm looking forward to going back to Iceland this summer for more of the same!
Updated 2021 : note that the above post was originally published in 2007, but is left here for archival purposes.