Mind the Gap

Visiting Nuremberg using the U-bahn (underground), the details of the modern carriages stand out.  I don't know the age of the current infrastructure and rolling stock, but I loved the level of detail. Look at the darker flap which moves out as the doors open, and stops at a minimal gap between the train and the platform.
Its smooth, quiet and comfortable. Extra shows the spaciousness and very clear information screens, which swap at each station to show all connection lines.