There was a stone hall by the river, built low and thick against the weather. People came to it from the surrounding lands, not because it was beautiful, but because of what happened inside.
In the center of the hall stood an iron cylinder, heavy and ringed, set into a cradle of stone. A rod fit closely within it. When black powder was poured inside and set alight, the rod leapt upward with force enough to shake the beams. Sometimes it struck the roof. Sometimes it bent. Each time it fell back hot and useless, and the air filled with smoke.
Those who watched were impressed.
They spoke of power. They spoke of what might be done if the force could be made larger still. They learned to pack the powder more tightly, to seal the iron more carefully, to send the rod higher with each attempt.
And each time, when the smoke cleared, the hall was quiet again.