It is called the because of it's shape. If you look at the Paris Underground it is square but the London Underground has tube shaped tunnels and stations. Even the trains are tube shaped, apart from the lines which go overground for quite a way like the District and Circle line.
Because of the circular shape of the tunnel bore. Londoners likened it to a tube.
The Underground, more commonly called the Tube.
It is an underground rail network underneath London.
It's usually called either the Underground or the Tube.
What is the Underground in London called? (answer - the Underground/the Tube)
In London Underground (tube) stations.
London Underground is known by Londoners as 'the tube'.
The London underground system is usually referred to as 'the tube'.
It's a small passage
The underground rail system in London is nicknamed 'the tube'.
The Central line is the current oldest tube stock in the whole of the London Underground.
The network is called, The Tube, as in: I often take the tube to travel round London, it is quicker than a bus on London's congested roads.
'The Tube'