Inside Mary's body, the castle's floor area was in the hundreds of meters in both width and length, with a height of eighty meters, divided into upper, middle, and lower levels.
More astonishing, the castle had lighting despite having no generator.
Only after asking did they learn that its power source was Mary's stamina.
For every unit of electricity consumed, Mary would expend an equal amount of stamina.
Mary could, by intent alone, redesign the castle's interior.
If she felt three floors were too many, or there were too many rooms, a single thought could turn three floors into one or more, or make rooms vanish.
In other words, the Paramecia Fortress-Fortress Fruit came with a subspace hundreds of meters long and wide, eighty meters high, which the user could freely control.
They did not know whether, as the user's strength grew, this subspace would expand, or remain fixed in size.
That question would have to wait for the future.
A pity the height was only eighty meters—if it were also in the hundreds, Mary could free up space to store the Grantaine itself.
Robin pulled the Boa sisters aside to discuss how to remodel the castle.
The space could hold a grand fleet.
With only five people, they didn't need that much; one level would do.
Since Mary could freely remodel it and appear inside herself, Robin decided to turn the castle into a second home.
Two levels would be left for treasure, and the remaining level would become a new home for the five of them.
Because they were still among Apayado's ruins, the four didn't rush to start the work.
After examining the castle, the group returned outside.
Then Robin and the Boa sisters worked together to store all the gold from the ruins inside the castle.
Kahn, using "fetching the Golden Bell" as a pretext, temporarily split off from them.
In truth, he slipped into the temple where the sky island's "god" lived and knocked everyone out with Conqueror's Haki.
Reading hearts and peering through memories, Kahn quickly found where the Jet Dials were stored and took them all—hundreds of them, extinct below but collected by the sky island's "god."
Beyond Wavers, Jet Dials had countless uses.
Even Enel's Ark Maxim relied on mounting hundreds of Jet Dials so, aided by lightning, it could fly from the sky to the moon.
In the original course of things, those Jet Dials would have been taken by Enel.
Now, Kahn took them without hesitation.
Lifting the hundreds of Jet Dials with telekinesis, he also, from extreme range, used telekinesis to take down the Golden Bell atop the sky-piercing vine.
"Master, are those also sky island dials?"
When Kahn returned—
At the sight of the astonishing number of Jet Dials floating behind him, the four paused their work.
Mary asked without thinking.
Robin stepped forward, picked up one, and examined it. "A type I've never seen—must be a special non-civilian sky island dial?"
"Mm."
Kahn nodded. "They're Jet Dials, extinct on the sky islands. Their thrust is many times stronger than Wind Dials."
He looked at Robin. "Be careful. Jet Dial thrust can't be blocked easily."
"I understand."
Robin nodded slightly and gave up on testing it for fun.
The curious Boa sisters did the same.
After storing the Jet Dials and the Golden Bell in the castle, they continued harvesting gold.
With Kahn's telekinesis, the gold buried deepest in the ruins floated up.
He guided it toward Mary.
Mary only had to touch it and a translucent white veil would wrap it, shrinking it visibly, then it would queue up and fly into her inner castle.
Once Kahn really applied himself, the ruins' gold was quickly stripped bare.
Next, Kahn led them to find the so-called "Lord of the Sky," the giant python.
He stunned it with Conqueror's Haki and they entered its body to scavenge more gold.
When they came out, Kahn quickly found the golden pillars that, in the original timeline, sky islanders would have given to the Straw Hat Pirates but were taken by Bellamy and offered to Doflamingo; all of it was shrunk and stored in the castle.
By the time the last of the gold was gathered, dusk was near.
Unknowingly, another day had passed.
They returned to the Grantaine and sailed away from Apayado.
While Robin and the sisters went below to prepare dinner, Kahn guided the ship into a cloud current, widening the distance from Angel Island and Apayado.
At this cloud-path's end was not a cloud cliff back to the Blue Sea, but a passage to the next island.
Sky islands differ from Blue Sea landmasses—there is no magnetism here.
To reach the next island, one must rely on cloud paths.
The cloud path Kahn chose, like Angel Island, led within the Summit of the Western Sky to Birka.
"Master, we're not going back to Angel Island?"
Carrying dishes, Mary stopped in front of Kahn—whose hands were empty—and used her fruit ability to enlarge the dinner set aside in her castle and place it on the open-air table, glancing at the endless white sea as she asked.
"Mm."
Kahn nodded. "Angel Island and Apayado are small. Two days were enough to see them. It's time to head to the next island and see what other sky-island specialties there are."
"I see."
Mary nodded gently and went back to help in the galley.
When Robin brought dinner out, she didn't ask where the next stop was.
Clearly, the girls had talked in the kitchen.
Studying the navigation map, Robin knew that after Angel Island came Birka.
She, too, looked forward to the next sky island.
But that hope was destined to fall a bit short.
Not every sky island is as special as Angel Island—with a centuries-old Apayado hurled to ten thousand meters beside it, the legendary Golden City, a Poneglyph, and even the Pirate King's inscription.
What made Birka notable were largely the Ark Maxim's design drafts, the practice of mantra, and methods to train Observation Haki.
If even Observation Haki training methods exist there, then clearly Birka's rulers and their guards possess superior strength—likely above Angel Island's.