On this Wiki I'm known as Remnant Echo though In-Game I'm called EpicLaggage.
This is a Guide to show everyone How to get to the Secret Area in the New Corpus Outdoor Endless Defense Map.
The New Corpus Endless Defense Map offers a Area for which Sniper's can Take Aim from. This area gives you a really good view of the surroundings, utilizing this would make those missions relatively easy.
How to Get There
First of all you'll need to go to the tall building, the entrance is to right of the Cliff View.
Once there you should be able to see what looks like a Broken Elevator.
Now this is the Hard Part, You'll have to go all the way up the Elevator Tunnel by using the Wall Jump Maneuver (Shift + Jump) along the Side of the Elevator.
After a tiring Series of Wall Jumps you'll finally reach the Snipers Reach.
Now that your at Snipers Reach there's a Couple of Storage Containers as well as Storage Boxes which can be looted.
How to Leave
Simply, you can jump down from the Area.
Or the alternative is taking a nice glide along the Zip Line while shooting Down Corpus.