Exactly. Such a basic thing today but how would they have done it? If they used candles or lanterns then the ceilings should be sooted up and then there is the question of if you do have enough candles or lanterns for tens of thousands of people then carbon monoxide would read its ugly head. And with no forced air ventilation it gets even worse. I have a gut feeling they didnt use open flame for lights. Maybe they used tech similiar to the Baghdad battery. I dunno, but the lighting question itself is fascinating.