After you defeat the golem boss in the starter area, Dragon Quest Builders lets you access the ruined Rimuldar continent.
The new area was showcased in a video released by the manga magazine VJump, and you can see it below.
Since Rimuldar has been hit by a devastating plague, the goal showcased in the video is to accomplish a quest provided by a local nun by building a place where she can take care of the sick. The building will serve as a focus for the rebuilding of the local village.
Gameplay starts at the 1:30 mark, and it ends at 14:30. Dragon Quest Builders launches in Japan on January 28th for PS4, PS3 and PS Vita.