Manholes are activated by walking over them to which a text—"I think this manhole leads back home!"—and sound notification and icon appear simultaneously after so.
Discovering manholes is also related to a silver trophy titled "Sewer Aficionado", which can be obtained from discovering all 13 of them.
Kat's Memo: A manhole on the island with the Karuwari Church where the sacred gem heist took place. This manhole's good for easy access to the far side of Auldnoir.
Kat's Memo: A manhole down at the bottom of the stairs leading into Pleajeune, right by the statue of the goddess holding up the burning fire of passion that symbolizes the district.
Kat's Memo: A manhole right outside Arquebus Academy and the statue of the school headmaster pointing at something in the distance with his left hand.
New Stormshield TowerEdit
Kat's Memo: A manhole on the Endestria pier close to the New Stormshield Tower, which is due to come online in a year.
Kat's Memo: A manhole at the base of the titled elevator near all the storage tanks in the energy plant.
Airship Fueling DockEdit
Kat's Memo: A manhole on the bridge close to the fueling dock for the airboat liners and the centrally located Stormshield Tower.
Loop Line Station #1Edit
Kat's Memo: A manhole in the plaza at the bottom of the ropeway outside of loop line station #1. It's near the building with the giant TV monitor.
Kat's Memo: A manhole opening right up into Freedom Square, near the base of the clock tower in Vendecentre.
Kat's Memo: A manhole located in the middle of all the skyscrapers, near the monument.
Loop Line Station #3Edit
Kat's Memo: A manhole in the plaza at the top of the stairs leading out of loop line station #3.