City & South London Railway

The City & South London Railway (C&SLR) is considered to be the first deep-level underground "tube" railway in the world. When first opened in 1890, it ran for a distance of in a pair of tunnels between the City of London and Stockwell, passing under the River Thames. The diameter of the tunnels restricted the size of the trains and the small carriages with their high backed seating were nicknamed "padded cells". The railway was later extended and became part of the London Underground system. Today, it forms the southern half of the Northern Line between Morden and Kennington, and its Bank branch.
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