I wasn't able to see it, though I had wanted to (grading hell, all weekend kept me chained to my desk). It's definitely unusual (almost unheard-of, I would say on the basis of my admittedly partial knowledge) for an Italian opera of the primo ottecento to have a ballet.

They all, however, have chorus. (It's Baroque opera seria that almost never has an actual chorus -- the final "coro" is an ensemble of all the soloists.) One oddity in this period is that the chorus is fairly often male-only (Barber of Seville and Rigoletto come to mind.)

All these stories of the knights of Charlemagne are, as Andrew said, part of the same long episodic saga -- I first read it as Part III of the collected "Bulfinch." Armida, Alcina, Orlando, Rinaldo... the stories go on and on. Even Huon of Bordeaux (see Weber's Oberon) links up to it.