Starts, like, 25 seconds in.
So Lysandre, crazy fuck that he is, tries to go full Hitler on Pokeverse and eradicate all Pokemon from the face of the planet because he's feeling a bit cramped. He and his masterfully executed flashback reveal that thousands of years ago, angsty sasquatch king decided to reap vengeance on the world for killing his starter, even though the dude managed to bring the thing back to life (wtf bro). Lysandre intends to use the same weapon, and he states that the sleeping legendary Pokemon's energy fueling that shit attributes to 99% of the thing's ammo.
Anyway, yeah, Kalos is based on France. As you can see in the video, it's pretty fucking big. Dunno if I can scale using the Earth 'cause it's much closer to perspective, but I can scale using France.
Edit: Using Flutter's scaling...
The blue line he measured was about 237px, or something.
(100/35)237=677.143km
(677.143/380)104.0433=185.4km
(185.4/62.626)327=968.0612km
A=pi*(968.0612/2)^2
A=736,030km^2