Boathouse

While the dinghies that are used to row the first years to the castle for the first time are only used one night a year, they still need a place to be stored. The boathouse is an underground harbor where the dinghies are docked, and while there's no way to get out onto the lake without a teacher's wand, the boathouse often serves as a place of quiet introspection for those who are overwhelmed by school.