From reports coming out of D23 Japan, a video exclusive to the convention was shown about the development process/progress of Kingdom Hearts III.
During this video a screenshot of the Tangled world was shown with Rapunzel in the Kingdom of Corona. This suggests that we will be able to enter and possibly explore the actual city.
This picture also pictures NPCs in the background... which looks like it means no more empty worlds in Kingdom Hearts, which as been a criticism of the series for many years.
This is also supported by IGN Japan's article (translated by MysticDistance on twitter), which can be found here.
More images from the 'Making of' video have surfaced thanks to UrePia, showing Sora walking around Corona (including the many NPCs), as well as a first look at the 'Giantland' content in KH3 (which appears to be a Game & Watch style mini-game):
'Making of Kingdom Hearts III' video shown Exclusive to D23