Something from my childhood memories.
Opened on 14 December 1896, it is the third-oldest underground metro system in the world after the London Underground and the Budapest Metro. It is the only heavy rail underground metro system in the British Isles outside London.
It is also one of the very few railways in the world with a track running gauge of 4 ft (1,219 mm). Formerly a cable railway, the Subway was later electrified, but its twin circular lines were never expanded.
The line was originally known as the Glasgow District Subway, but was later renamed Glasgow Subway Railway. It was so called when taken over by the Glasgow Corporation who renamed it the Glasgow Underground in 1936. Despite this rebranding, many Glaswegians continue to refer to the network as "the Subway". I understand that that name has now officially been reinstated.