Cathardia

Cathardia (, lit. "Stagnated Euphoria") is a sky archipelago territory under the control of the Marines, and officially known as G-10 (海軍G・L第10支部, Kaigun Gurando Rain Dai-Juu Shibu) — part of the G-Base collection created by the organization. According to Ein, he discovered the island in the past as a Commodore, acting as his vacation spot and enjoying the peace of nature, which he longed for sometime after becoming a Marine. Upon the creation and growth of the Marine Winged Squadron, he looked for a place that would best suit his needs, thus decided to give up his secret place for the good of his subordinates — seeing how it met his requirements.

Overview
A series of Sky Islands located at the ends of — a few miles off from the, it's considered to be tranquil, as Ein was often at peace and felt closer to nature — temporarily bringing up peaceful memories of his Skypeian days, which he counts as "fleeting dreams", and giving him a greater yearning for staying on it. Due to being located high above the atmosphere, it's usually inaccessible to those incapable of flight, thus a perfect secret spot in most Marines and Pirates were "flightless". In addition, despite it located in an area with chaotic weather, it possesses a nice and soothing atmosphere — only being cold and containing low oxygen levels because of its elevation; however, coldness was replaced with warmth because of Ein's presence on the island, with the current temperatures adding on to its tranquility.

Like other Sky Islands, there's an abundance of greenery and some fauna, however, strangely enough, the archipelago seemed different from its kind, as if it was made artificially, seeing how multiple rock fragments stay afloat. When explored, Ein discovered that it was originally an island that dwelled in the sea but was suspended due to a combination of a and powerful surges of  resonating deep within the sea, which erupted as a concentrative burst for unknown reasons. At the bottom of each floating island, there's a hole where Haki constantly flows outward; only those with Kenbunshoku Haki honed over many years would pick up on it and use it to reach the island.

Upon making the island his new base of operations, over the years, Ein has transformed the island into a functioning Marine base with various facilities and housing while finding a balance between man and nature; this profound respect for nature spread to his subordinates as well, who constantly take care of the plants and wildlife on the island. It seems that since the islands are close together, travel between them is trivial. Due to Sabaody being close by, the Winged Squadron would often patrol the lower archipelago as part of their routine, doing their best to suppress incoming pirates and illegal activities whenever they present themselves.

Trivia

 * Most of the locations and constructs are based on the various Azrael bases in the Underworld from the manhwa, Soul Cartel.