When you’ll reach at the destination point, you’ll find a vault in the ground with four buttons near it. That base is actually located in a cave under the mountain that you will be standing on top of. The indicator will point towards a military base but don’t worry about the reinforcements. To get to the teleportation gate, simply go to the location marked by the player’s indicator on the map. You can access it if you know the code to unlock the huge vault doors hiding it. Teleportation gate is one of those secrets which allows you to teleport to different locations. Just Cause 3 contains many secrets hidden in the massive country of Medici.