Tube bosses have defended a decision to close two underground lines by giving journalists a tour of the tracks.
The whole Circle line and the District Line between Earls Court and Whitechapel will shut for repairs for 12 weekends between 1 May and December.
District Line manager Bob Thorogood pointed out problems from the driver's cab, explaining that parts of the track dated back to the 1860s.
The poor condition of some sections means 10 mph limits are imposed.
Driver Clynt Sandford, who was also on the tour, said: "The system has deteriorated considerably over the last 20 years."
Track, ballast and sleepers will be replaced during the major renewal programme which London Underground says will mean a smoother journey for passengers.
No work will be carried out during the weekends of the Wimbledon tennis championships or during the Notting Hill Carnival.
The line will also shut for five weekends in 2005.
Sections of both lines had to close over the weekend because of a collapsed drain at central London station Victoria, which threatened to flood part of the network.