The photo above shows the four ovens in which the gunpowder was "cooked." I'm afraid I'm a bit unclear on the process...I was too busy taking pictures and missed the explanation!
Local myths claim that there were underground tunnels that led from the pulo all the way to the sea (2 kilometers away) and that the gunpowder was carried through them to be loaded onto ships for transport. Tunnels leading inland have been discovered in the historic center of town, but what remains of them does not lead very far, so this myth remains unproven.
By the end of the 1700s interest in the gunpowder factory was already declining and the structure was abandoned and allowed to fall into ruin.