The Sewers - Stardew Valley Wiki
The Sewers are a location in Stardew Valley. The area can be unlocked by obtaining the Rusty Key after donating 60 items (artifacts or minerals) to the Museum. They can be entered either through the sewer cover in the south of Pelican Town or through the grates in the south of Cindersap Forest. Krobus is also located here and sells rare items.