The island with only roads on it

the island with only roads on it, the one you can only get to by placing 15+ explosives around you, time travel or something else, while the playable area is uneffected by this time destorion because it’s under a dome of protection, it’s like something from the outer limits tv show, spooky

Which one?
There are two unused islands with roads shown on the map.

Both are unreachable, as they are locked “dlc-content” (as the game says). And no, as Carni and other officials often stated, there are no officially released plans of making them accessible.