After having completed the game, you'll be able to replay all stages. The area is located The Amazon. To be able to access it, you'll have to have a 7 in the ten thousand's place of your money before stating the area.
Once this is achieved, you'll start the area on the rope of the helicopter rather than beside Launchpad. You'll then jump off and start the stage in the "area in the clouds" and then the achievement is yours.