In order to find completely new areas, try completing the NPC Quest. The reward for that quest is finding Overworld Station, an access point to the new area DRAWER.
Another key access point is the second Windmill. The rock sign at the base of the windmill hints that there is a second tower nearby; you will find it by exploring to the east. The second Windmill leads to BLANK, the 47 Card Gate, the second Nexus, and the Debug World.