The Laundry Pool is a location within Clock Town in Majora's Mask. It is the southwestern part of the city and is only accessible from South Clock Town. It is also the smallest part of Clock Town, being smaller than the other four cardinal directions. A Stray Fairy can be found hovering above the pool during the day, Link can catch it and bring it to the Great Fairy in North Clock Town.
On the Night of the First and Second Days, Guru-Guru can be found at the Laundry Pool spinning his music box. If Link listens to Guru-Guru's story the whole way through, the man will reward him with the Bremen Mask.
Anju and Kafei
The Laundry Pool plays a part in the Anju and Kafei quest. After Kafei had the Sun's Mask stolen from him by Sakon, he could not bear to see his love, Anju without the mask. So the Man from Curiosity Shop kindly allows him to stay in the Back Room behind the Curiosity Shop (accessed through the Laundry Pool area) for as long as he likes.
Kafei spies on the customers of the Curiosity Shop, hoping to find Sakon among the patrons so he can follow the thief back to his hideout. On the Night of the Second Day, Sakon drops by the shop and Kafei stalks after him. Link will receive the Keaton Mask from the Man from Curiosity Shop and then, on the Final Day, him and Kafei begin their quest to take back the stolen mask from Sakon at Sakon's Hideout in Ikana Canyon.