Why didn't the Roseguard ever find other levels?

[Grumpus]

I understand that in the main structure, the stairs down in area A12 were hidden well, and that the entrance under the dock may have been hard to spot.
But the building on the little island to the north has unhidden stairs down(A21), and on level-b also has unhidden stairs down (B5) (in addition to the hidden stairs in B2).
Did the Roseguard just never bother to explore the other building? Even though they built a town here, wouldn't someone be curious at some point to find out what was in that structure?

Anyway, just wondering if I missed an explanation.

[Haydriel]

I think they just went in, killed Belcorra and retired. No need to explore the ruins as the big bad was dead.

In the years after I think the legends of Gauntlight being a haunted ruin (?) kept most explorers away. Or maybe Tangletop/Mr Beak kept them at bay?

[Grumpus]

Maybe, but they weren't "ruins" at that time, right? I assume that the buildings were in good shape at the time of the final fight and contained possible valuables or insight into whatever Belcorra was up to. Surely worth a gentleman's peek inside at the minimum.

[aghull]

The entrances into the lower levels are hidden. Belcorra clearly planned to be able to hide parts of the gauntlight. She even murdered her own servants upon learning of the Roseguard attack in order to cover her tracks. She may even have deliberately gone up to the first floor to meet them just so that she could prevent the true nature of the Gauntlight in the lower levels from being discovered, even if she had to die to do it.

Why is there a "floor" on the level 1 "base" of the lighthouse itself, rather than just one giant open column. It seems like structurally there's no reason for it, but perhaps it is intentional that the lighthouse plausibly appears to be just a "normal" lighthouse with nothing underneath it.

[Grumpus]

aghull wrote:

The entrances into the lower levels are hidden.

Not in the small building to the north. The stairs down are just behind an unhidden door.