Just Cause 4 features many Easter Eggs including quite a few new ones that have not appeared in previous games. There are some easy Easter Eggs that have made a return such as car number plates and references to Scorpion but we are only looking at the new ones in these guides. The really cool ones are a little trickier to find and you have to know where to look.
Below you can watch videos that show exactly where you need to go to find them. There is a single video with them all included and individual videos if you are looking for a specific one to save you time.
The trickiest one to find and actually get into is the secret mountain moon base but hopefully the video below will help you reach that. It's not easy and we lucked out and managed to make it inside the mountain hideaway on the second attempt.