Note: This could be a spoiler if you haven’t seen the episode yet. Be warned.
Henry found a glass piece in the mineshaft (We know it was a piece of Snow White’s coffin from Fairy Tale Land). In the final scene, we see that Regina somehow found it and brought it to the service elevator shaft:
She drops it down the elevator shaft (very lost hatch shaft like, btw):
then, the piece of glass coffin lands right on top of the glass coffin in Fairy Tale land. The entire land seems to be underneath Storybrooke Maine.