Lake Mobius (メビウス湖, Mebiusu-ko, or 巨大湖メビウス, Kyodai-ko Mebiusu—lit. meaning "Giant Lake Mobius") is a massive lake in the center of the Dark Continent. It is conventionally divided in three sections: "Human Territorial Waters", which encompass the relatively diminutive territory occupied by mankind, "Untamed Waters", where the New Continent is located, and "Dark Waters". The latter two are divided by the "Border Waters", an area where passage is regulated by the Gatekeeper. However, the public at large is aware of a different partition, that of "Territorial Waters" and "Uncharted Waters", which in reality accounts only for the two bodies of water before the Gatekeeper's territory.
A map showing the surrounding area of Lake Mobius is presented in King Nasubi Hui Guo Rou's video declaration of him financing an expedition into the Dark Continent. Another Lake Mobius map is used in a conference with the newly assigned Deputy Secretary Steiner of the Restricted Voyage Agencies and V5. Steiner uses the map as an example of how many times that is on record, humanity has attempted to go to the Dark Continent. In Ging's explanation of the V5 trips made to the Dark Continent, he uses a map of Lake Mobius of the locations of the routes they took and he later mentions someone who tried to explore the entire lake and wrote a book about it.