Inside the sphere, he finds a large sea of translucent foam, and has a conversation in his thoughts with some sort of entity that speaks in cryptic riddles, who eventually tells Johnson that the greatest power humans possess is the ability to imagine things.
Magny-Cours is located in central France, approximately 260km south of Paris and 240km north west of Lyon, near to the city of Nevers. The nearest airport of significance is Clermont-Ferrand Auvergne Airport, around 1 hour 50 minutes drive to the south.
Mags is an old female victor from District 4. She is also the district's tribute during the 3rd Quarter Quell, because she volunteers in the place of Annie Cresta. Since she is so old, it is likely that Mags volunteered to save Annies life, much like Katniss Everdeen choose to save Prim's rather than for the chance to compete.