Mikau Lake is a location in The Legend of Zelda: Breath of the Wild. It is located in the Lanayru Great Spring region in the province of Lanayru. It is located northeast of Zora's Domain and southwest of Lulu Lake near Ploymus Mountain.
Like many locations in Breath of the Wild, Mikau Lake is named after a character from a previous game, namely the Zora guitarist Mikau who's spirit was transformed into the Zora Mask allowing the Hero of Time to transform into a Zora.
Its closeness to Lulu Lake may also reference the strongly implied romantic relationship between Mikau and the Zora singer Lulu as he is believed to be the father of Lulu's children explaining his attempt to rescue Lulu's eggs from the Gerudo pirates which lead to Mikau's death. Alternatively it could simply be a reference to Lulu and Mikau being bandmates with a strong bond. It should also be noted Toto Lake is located northwest of Lulu and Mikau Lakes which is named after the The Indigo-Go's (Lulu and Mikau's band) manager Toto and its distance likely references Toto being away from Zora Hall during the events of Majora's Mask.