Beanbean Castle Sewers is a location that appears in Mario & Luigi: Superstar Saga.
Being the sewers underneath Beanbean Castle, the area is mainly metallic with many pipes around.
Mario and Luigi were sent to Beanbean Castle Sewers by Lady Lima to fix the plumbing to prove they are the heroes. They must hammer the various of leaks in the pipes to fix them. After fixing the plumbing system, Lady Lima compliments them. Mario and Luigi told her that she threw tem into the sewers. Lady Lima became puzzled, she assumed that Cackletta was attempting to capture the Beanstar. They realize Cackletta disguised as Lady Lima and took down the force field protecting the Beanstar.