I feel that Lodestar is the "entrance" to Laugh Tale (or the old entrance to the "Great Kingdom" of the Void Century). After Vegapunk revealed that the sea level already rose up by 200 meters in the past, it's plausible to think that the "Great Kingdom" was a much bigger landmass than anyone ever imagined... if this is true, Lodestar and Laugh Tale, now separate islands, would be connected 800 years ago. Therefore, if Lodestar is the "gateway", then there'll be strong remnants of that ancient civilization when the SHs get there, as Inu already anticipated.