tsubaki
Player Valuation: £90m
Roman legions wasn’t it ?
Some were, others were built by engineering teams that were probably a mix of citizens, freedmen and military personnel. There might have been some slave labourers involved somewhere (more likely in Italy than the provinces), but in no way could you describe them as being built by slaves.
Saying “slaves” is completely misleading anyway as in the classical context the meaning is not at all the same as what slavery between 1520 and 1850 was like. To take petes earlier daftness as an example, if you were a slave in the Colisseum you were far more likely to walk away at the end of the day compared to the criminal who had been sentenced to fight you.