Paul Terry wrote:
In message , Jarle H Knudsen
writes

If, when visiting London as a tourist in August, I should like to ride one
of the underground lines in its entirety, which line and branch would you
suggest, and why?

In addition to the excellent suggestions from others, it is worth taking
a look at Baker Street, one of the oldest of all "underground" stations,
where the Circle/Hammersmith & City platforms have been restored to
something approaching their original appearance - given all sorts of
modern operating restraints.

Also, if your definition of "underground" is broad, then take a ride on
the Docklands Light Railway from Bank out to Greenwich (Cutty Sark). If
you position yourself right at Bank you can sit at the front of the
usually driverless trains, in a "driver's eye" position" and enjoy the
very steep climb from deep-level Bank to above the rooftops as you join
one of the oldest viaducts in London - then enjoy the spectacular views
of Docklands before plunging under the river to Greenwich.

Not to mention the really strange contrast of moving from the granduer
of the city to council blocks in a few minutes
HTH Phil