Here are the steps:
1.Enter the no cops cheat
2.Drive to the unmarked pay and spray
3.Lower into the underworld using the jetpack
4.Mark off the restricted area and fly there
5.You will see the rooms in the black project
6.Look for a solid floor and land on it
7.Vwalla...You are now in Area 69 underground base!
Notes:
1.There are no UFOS, Aliens, Monsters Myths ETC.
2.There is a minigun in a room near a radar room
3.There is a shotgun Near a lift door
4.There are no secret vehicles in the underground base
5. There is a map in the radar room
Anyone who creates rumours about aliensor myths in the base you will be reported to Pyr0xide