Thanks to the latest update, 1.04, removing the infinite loading screens that had previously still served as barriers to fully exploring some of the areas beyond invisible walls, YouTuber Caelum Rabanastre XII/XV was able to walk to Gralea (well, where it should be anyway)
during the day:
The fall into the caldera at 1:08:10 in the second video was incredible. I was not expecting it to have a solid bottom if you land in the right area. Also, take note of what's shown on the minimap as he runs across the bowl.
Also, YouTuber Tou Moua flew to Insomnia after escaping the boss battle during Chapter 9:
As previously confirmed, nothing is there but the suspension bridge and city wall at this stage of the game.
Also, here's some out-of-bounds exploration from YouTuber halo1crysis at the Disc of Cauthess: