How low do tube lines go?

This diagram visualises the deepest platform at each station across the London Underground network. The platforms are categorised by the Tube lines, including all except the Circle line, which is not covered by the data. With a quick glimpse, it’s obvious the Underground mostly does run below the ground. The deepest platform in the network is Hampstead, at over 58 metres below the ground. But there are other very deep stations as well—for example, Holborn (-41.1m) and Covent Garden (-37m) on the Piccadilly line, and Angel (-35.6m) on the Northern line, which has the longest escalator on the Underground network.

But not all the platforms are underground. Greenford station, for example, is more than 10 metres above ground. It was notably the last station to have a wooden escalator, which was used right up until 2014.

But then, how low do the Tube lines go? As this chart aims to show only the deepest platforms at each station (not all platforms), the line with the most deep stations is probably the Northern Line, which also includes the Hampstead station platform. The shallowest is most likely the Hammersmith & City line, running pretty much on the ground with equally as many stations above as below the ground. Its deepest station is less than 7 metres below the ground.

If you are keen to find out more, Tube Alerter has done comprehensive research on the subject, including their own take on the data.