Great micro car analogy: small, simple, light, cheap, fun but dangerous if you take liberties.
Good Planetarium analogy, yup a bit like that or an Orery. The inner and outer vertical shafts will have pulleys and belts to 2 vertical counter-shafts. The handle will be on a shaft with two worm gears, these will drive two spur gears of different sizes, one on each counter-shaft. That will ultimately give two "layers" of model going clockwise at one speed and two more layers going anti-clockwise at another speed. The models show transport by water, rail, road and air.
Once that is done it will be time to get the "layer" base-boards made and fitted (the basic structure of the hill part of "Sleepy Hill". THEN it will be time to start making the cams and bell-cranks to work the non-transport models and just hope not too many mechanisms snag on too many other mechanisms! Exhausting work, brain hurts!