Human sacrifice in ancient Rome was rare but documented. After the Roman defeat at Cannae two <answer>Gaul</answer>s and two Greeks were buried under the Forum Boarium, in a stone chamber "which had on a previous occasion [228 BC] also been polluted by human victims, a practice most repulsive to Roman feelings". Livy avoids the word "sacrifice" in connection with this bloodless human life-offering; Plutarch does not. The rite was apparently repeated in 113 BC, preparatory to an invasion of <answer>Gaul</answer>. Its religious dimensions and purpose remain uncertain.
Before the invasion of what area was human sacrifice carried out?
Gaul