The Copenhagen metro is one of the most well run metro systems in the world. It is completly automatic and runs 24 hours a day. It never stops running, not even for maintance. To maintain it they close of one of the two tracks at night and put the this part of the system into maintance mode. In maintance mode the trains run at reduced speed along the the operating track while the other track is worked on. If the maintance zone is so long that the 10 minute interval of the night train service can't be kept over the single track section, then a shuttle train service will run on this part while either side will still run a normal every 10 minute service.
The metro trains go 50mph and have the same awesome VF as Manchester tram 2000 and the original Birmingham tram (both of these have been replaced) making this VF drive on the Copenhagen metro a rare sound.
This system works well but is a bit slow.
Copenhagen has an interesting selection of buses
Cheap flight adventure
Copenhagen was the very first place I went on a cheap flight adventure, this was infact the very first time I had been on a airplane and rather than do a normal sort of trip, I did a nigh trip where I went out in the evening and came back in the morning the next day. This made it into an adventure. A few months later I went back to Copenhagen in the daytime with TopLevel.
The following video is of the lifts at the metro station in the middle of the night from my first trip.