Trying to get the achievements for discovering all locations and there is one part near the end of the area I can't find anyway of getting to
You'll need to do the mission The Cold Shoulder (given by Scooter) in order to gain access to the Rat Maze. According to the wiki:
Entry to the Rat Maze is barred on initial entry to the Fridge and becomes accessible when pizza and flowers are placed for Laney White in The Cold Shoulder.
Once you've gained access the the Rat Maze, you will be able to get to Crystal Claw Pit
The Crystal Claw Pit is a large open area at the end of the Rat Maze.
and the Rakk Cave.
This area is elevated well above the floor of Frigid Cleft near the Outwash gate. It can be accessed by fighting through the Rat Maze...