i havent heard about this dungeon thing, where is it?
2 years ago (+1)
In this game, there have places call 'dungeon which have a dungeon grid map at the left of the screen like this. 
Each dungeon have various map and level. As I remember, there dungeon exist in Wolves den, Uphill cave, Plain of death, Junkyard, Misty lake, etc.
I think the dungeon you mentioned is Junkyard dungeon since this current update (0.44) have a Junkyard updated content.