Wargames Foundry Ballista and crew, with an old Airfix wooden watch tower. I like the low dawn/evening light in this shot. The crewmen are in late Roman or Byzantine costume. The ballista was an artillery device, a bit like a big crossbow, which involved two cylinders in which were long wound ropes of hair or sinew, which would provide torsion for a bar thrust through the ropes. Modern reconstructions of these have proven to be not just powerful, but very accurate indeed.