An ergastulum was a Roman workhouse building used as a type of factory with slaves held in chains or to punish slaves. The ergastulum was usually built as a deep, roofed pit below ground level, large enough to allow the slaves to work within it, and containing narrow spaces in which they slept. Ergastula were common structures on all slave-using farms (latifundia). The etymology is disputed between two possible Greek roots: ergasterios "workshop" and ergastylos "pillar to which slaves are tethered."