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The island possesses a massive caldera, with several rocky outcrops, which the Marines converted into outposts. The basin of the caldera is below sea level. Around the center of the caldera is a volcano-shaped geyser, that continuously spews out sea water. When night falls, the geyser in the middle of the island spews a mist of seawater, which settles in the Caldera's basin. This mist nullifies all Devil Fruit powers. As pointed out by Komei, Nebulandia is a bad place for people with Devil Fruit abilities to enter.
The island contains a vine-like plant which feeds on sea water. As such it possesses the properties of Seastone. For unknown reasons, the plant is triggered by Devil Fruit users and will try to wrap around them, which will weaken them.
Komei captured Zoro, Sanji, Porche, and Hamburg and took them to this island, and the other Straw Hat Pirates as well as Foxy and Kansho went to rescue them. Komei nearly succeeded in capturing all the Straw Hats and nearly killing Luffy. However, Brook, Tony Tony Chopper, and the other Foxy Pirates came to the rescue, along with the Kinoconda, whom they befriended on Mushroom Island. The pirates fought off the Marines, with the giant Kinoconda causing massive damage to the outpost, whilst Luffy faced off against Komei. During their battle, Komei, in a move of desperation, broke the caldera walls to let sea water in, in order to weaken the Devil Fruit users, though this completely wrecked the base. However Luffy, together with Foxy, managed to drain the sea water, before the Straw Hat captain defeated Komei with his Red Hawk. The pirates then left Nebulandia, returning to Mushroom Island.