The Jubilee Line is one of the tracks of the London Underground. Originally it ran from Stanmore to London Bridge, but now it's been extended to the East End.
Since its renovation it has become one of the most reliable lines on the network - almost as good as the Doclands Light Railway. The new section has is remarkable not only because of the fabulous architecture - but also the safety featues - like platform doors that prevent junk and people from falling into the path of trains.
On the tube-maps it's coloured grey. It's one of the longest lines with no branches running from the North-West to the South-East passing through the shopping areas of London's West End.