I visited the London Transport museum in Covent Garden last weekend (Feb 2020) with my young grandchildren and they really enjoyed being able to touch the exhibits and in lots of cases climb stairs on buses, sit on seats in carriages and just generally touch everything. I enjoyed it too especially the small exhibition on abandoned stations or stations that never were actually built.
One quite surprising bit of information was that the zero point for all measurements on the tube network is the buffer stops of Ongar station which used to be the furthest eastern point and terminating station on the Central Line. The strange thing is that it isn’t on the tube network anymore, it was closed in 1994 when the Central Line was cut to terminate at Epping.
All distances have been and still are calculated from that point since metric measurements were introduced on the network in 1972. I guess the cost of changing it to a different station would be too much to change.
Ongar station though fortunately is still being used as it is part of the Epping and Ongar preserved railway and is definitely worth a visit, and it has the advantage of not being too far outside London. For more details see their website here.
The video above is from a visit in October 2016 and is filmed from the platform of Ongar station.