The Helsinki Metro is not large, really just one line but it has unique trains and they run on traditional gravel pad track (rare) and it’s the northernmost subway in the world.
There are three generations of rolling stock in the system, I really wanted to see the oldest Mark I Bombardier trains but every single ride I took ended up being on the new Spanish Mark III train.
The system was probably the cleanest and smoothest I have ever ridden, including Tokyo, I really liked it.
A Bit Gone 