The Way of the Fly

On the wall inside a cylindrical glass container, three centimeters from the upper circular base,
there is a drop of honey. On the lateral surface, diametrically opposite it, there is a fly.

Show the fly the shortest route to the honey.

The diameter of the cylinder is 10 centimetres and the height 20.

Don’t expect the fly to find this way itself and thus facilitate the solution of the problem: for that it would have to be well versed in geometry, and that is something beyond a fly’s ability.