When Caesar came in Lutèce, this one was a very little town composed of huts gathered on an island in the middle of the Séquane. But the Parisii, Gallic people, were galvanized by chief Vercingetorix: they started to oppose to Caesar's conquest! In -52 began the Lutèce battle.
So it was the beginning of the "Roman peace": with it, an unequaled prosperity. They started to raise buildings everywhere in Lutèce! Right bank of river Seine was an inhospitable swamp, so Lutèce extended on the other side, on mons lucotitius overlooking the Bièvre valley: here, a new city was born!
Lutèce became very important and people came from a long way to see the amphitheatre newly raised. So, let's see this building! Its enclosure is 56 metres in diameter! Compare to, just imagine the theatre of Rome is 59 metres... Row of seats didn't completely surround the enclosure, because in front of that, we have a vast scene. Each seat on those rows was named after its owner. We count 10 000 spectators, maybe more.
But Lutèce was invaded by Barbarians; in the end of the 3th century, the city was completely destroyed. Romans then decided to fortify it, in order to give it a more strategical importance. To raise those walls, they used ruins, especially our amphitheatre's ones. And in the 6th century, the theatre was rebuilt.