Today saw the launch of Season 4 in Fortnite Battle Royale, and a lot of changes have happened on the map for the new season. One of those changes is the addition of a hidden bunker/command centre that is located under the house in Salty Springs.
Secret underground bunker/command center found under the blue house in Salty Springs from FortNiteBR
As you can see from the Reddit post above, one of the ways to access the Command Centre in Salty Springs is to drop in the hole found under the stairs.
Another Reddit post shows another Command Centre in a new area, south of Lonely Lodge:
There is likely to be more Command Centres around the map and could possibly be a new challenge in the upcoming weeks to visit them.
Let us know if you have found any more of these Centres in the comments section below.