Beginning in the early 1890s various inventors tried putting bicycle gears at the bottom bracket. Probably the most successful (least unsuccessful?) was Adler of Germany in the 1930s.
One on display @
https://onlinebicyclemuseum.co.uk/19...-gang-typ-155/
For a variety of technical reasons this is pretty much a dead end...well, except for those Effigear, Pinion and Sturmey-Archer gearboxes in current production!