In the light of my fairly-recent interest in Tube Challenging, I have something of a desire to go and do Helsinki too. I've never even used the Helsinki Metro before, but it's route layout isn't exactly complicated:
http://upload.wikimedia.org/wikipedia/c ... ro-map.png
If you want to travel abroad for some Underground Challenging and New York is too expensive, how about a short hop over to Helsinki? Flights are as cheap as £90 each way, and it's a wonderful and beautiful city.
This photo of a Metro train sums it up for me:

I can't think of anywhere on our Underground network with scenery as stunning as that.
Anyone interested?
...Alright, I don't expect anyone to be interested. But I wanted to tell you about this anyway
