Erumalu was a town located in Arabasta.
Once called the Green City (緑の町 Midori no Machi?), this town was ravaged by the encroaching sea and the extended drought, the latter caused by Crocodile's use of Dance Powder. The inhabitants have long since fled and the buildings are falling apart.
Erumalu is currently nothing more than half-buried crumbled buildings and dead trees, with some skulls laying around the sand. There was once a canal that distributed rainwater around the city, but the constant drought created by Mr. 0 and the Dance Powder eventually caused the water reserves to dry up. According to Vivi, Erumalu used to be much richer in plant life.
The town once used to rely on water from the Sandora River in order to prosper, but as the river began losing much of its force, seawater from the Grand Line's ocean started inflowing, taking over part of the river's course and turning the water unusable for consumption or crops. A sign of the seawater overcoming Erumalu's portion of the river was the presence of a pack of Kung-Fu Dugongs, a marine species of animal, near the town's ruins.
Without the river, the citizens of Erumalu became dependant on rainfall for survival. Because of the drought orchestrated by Crocodile, however, Erumalu could not resist the lack of water and was abandoned.
The Straw Hat Pirates docked near Erumalu's ruins from the Sandora River, following Nefertari Vivi's plan to reach Yuba so they could reason with Koza's rebel army. At the riverbank, Usopp was attacked by a Kung Fu Dugong, which then lost to Monkey D. Luffy and was converted into his apprentice. A short time later, Luffy had already managed to tame an entire pack of the dugongs, with them showing up to assist the Straw Hat Pirates later in the arc.
At Erumalu itself, Vivi began explaining about the town's history and her country's situation. Hearing about Crocodile's scheme resulting in the slow destruction of their friend's country, Luffy, Sanji and Usopp vented some of their anger on the remains of a destroyed building, with Luffy declaring their resolution to defeat Baroque Works.
- According to Kappa, there's an unnamed village near Erumalu that's also suffering from the drought and where a sick friend of his lives.