GTA 5 Mt Chiliad Mystery: Unlocking Fort Zancudo

Fort Lago Zancudo is a U.S. Military base located on the outskirts of the Lago Zancudo swamps and at the base of Mount Josiah in Blaine County, San Andreas. It closely resembles real-life Vandenberg Air Force Base in Lompoc, California. Lago Zancudo's marshy environment suggests that Fort Zancudo is also based on that of real-life Naval Base Ventura County, Mugu Lagoon.

Map Of Fort Zancudo

Perimeter Fence Signs

Collision Model image of the Zancudo buildings

The Bunker and Control Tower locations

Collision Model image of the Zancudo buildings

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You are able to commandeer different vehicles & aircraft at Fort Zancudo.

Locate the Vehicles & Aircraft at the above locations

Cargobob Helicopter

Buzzard Helicopter

Titan Plane

Rhino Tank

Crusader Jeep

Barracks Truck

P996 Lazer Jet

Front & Rear Entrances:

Ramming of the gates results in instant wanted level stars.
There are also CCTV camera's at the entrances, but these can not be destroyed like the Control Tower ones.

Front Gate

Front Gate CCTV Camera

Rear Gate

Fire Station:

Front of Fire Station

North East Side of Fire Station

Soldiers that can sometimes be found sitting at the rear of the Fire Station

Treatment Works:

Treatment Works Entrance

Control Tower:

Control Tower Entrance

Collision Model image of the Control Tower

Control Tower Top Floor

The Control Tower is located in the Northern side of the base.
Inside the tower you will find a lift on the ground floor & also near the top of the tower.
Forced entry to the Control Tower has been achieved using a number of methods. Solo, & also using the hangout option with all 3 characters.

Hangout option screenshot

The hangout characters will not advance past the stairwell entrance. They will fire back to protect you & themselves.
Using Chop in this situation results in him not advancing past the stairwell entrance & will head home if Franklin (your character) reaches the top of the tower, due to him being too far away from Chop.

The No wanted level/stars entry to the Control Tower

The 'take control' UV map clue

It has been speculated that the UV map with the 'take control' reference indicated on it points to taking over the Control Tower.
It has also been suggested it only points to the mini gun that can be found in the office near the top of the control tower.
Attempting to take control of the Control Tower with wanted level/stars achieves little. The soldiers will just keep re-spawning & you can not lower your wanted level by hiding out in the tower, similar to the bunker method.

Mini Gun in Control Tower Office

You will need a Buzzard Helicopter to parachute out of to gain a no wanted level/stars entry into the Control Tower.
Select an angle from Mount Josiah to parachute in from at NIGHT.
Ensure to ready your character with the appropriate SILENCED weapon of choice before beginning.
The selection of stealth clothing & black parachute are preferred to minimize detection.

Stay low & as close to the ground when over the base to avoid being detected.

Enure to have a silenced weapon ready on your character to shoot the Control Tower entry door guard as you parachute in before he raises the alarm.
You must land right infront of the tower front doors to ensure no alarm is raised.
Use the landing with your feet up is the best option.

After entering the main entry doors with no alarms or wanted level you will be confronted by 3 randomly chosen game characters which you must kill before they scream & run from the tower raising the alarm.
I have encountered teen boys, middle aged men & women when entering the tower.
These characters replace the usual 3 soldiers who exit the building when trying to enter with wanted level/stars.

Various spawned peds you can encounter

After killing the spawned people inside the entry hall, you will need to destroy the 11 CCTV Camera's scattered throughout the Control Tower.
You have a 3 SECOND WINDOW before they sound the alarm after viewing you.
Note: only 10 of the 11 camera's are monitored from the front entry hall reception area.
The first camera is to the front left corner as you enter the building. It is suggested you shoot the random people first, then shoot this camera & move over over to that camera side so you can avoid detection by the hallway camera above the stairwell.

Move your way up the Control Tower taking out all the CCTV cameras along the way undetected. You will encounter a number of soldiers in the tower making your way up to the top.

The 10 monitored CCTV cameras

It appears the only CCTV camera not monitored at the front entry area is the office camera?
On some occasions you will find a soldier who appears to be surrendering in the office?
No interaction can be obtained from any of these characters, & if you move outside of viewing range they will disappear.

Surrendering Soldiers

On reaching the top of the tower you may encounter a soldier that appears to be higher ranking soldier & trying to look out of the tower with binoculars.
He will be accompanied by 2 armed soldiers. If you kill the 2 guards he will quickly pull out a weapon & shoot you.

The best place to do a quick save is in the tower elevators.
If you save at any other point within the tower, when reloading that save you will find a soldier right in front of you, who will hit you with their gun after loading the save killing you instantly.

Note there is a down button inside the top floor & ground floor elevator? This could suggest that this elevator is able to go down if triggered correctly.
Shooting of either lift buttons or trying to use it via the D-Pad has no effect. Could this lift be linked to the bunker lift?

Ground Floor Lift Entrance

Ground Floor Lift Interior

Control Tower Rooms:

Ground Floor Training Room

Computer Room

Office

Control Tower

The Bunker:

Front Entrance

Collision Model image of the Bunker & buildings

Inside Bunker

The bunker is an interesting POI (place of interest). Inside the bunker you will find an elevator that indicates the level -1 on the level counter above it. This indicates that the elevator is at a level 1 floor down.

Lift level at -1 & down button on panel

This bunker is also the place that the Fort Zancudo UFO sits above.
At the times between 1am & 4am a light show can be seen on top of the bunker from that UFO. The image below is the final pattern at 3-4am.

Zancudo UFO 3-4am light pattern on the Bunker roof

You are able to see this light show from inside the bunker.
The entrance to the bunker also has a red flashing light that sits above the doorway & will flash when you have been detected.

The elevator doors have been opened using an online content creator glitch & a no door mod as shown below.
This leads me to conclude that these doors can be opened in single player mode & accessed if triggered correctly.