The Foyer is the first room in Luigi's Mansion. It is locked until Luigi defeats the Gold Ghost that has the key. Inside, Toad is fretting over Mario's disappearance. Luigi tells Toad he will find Mario, and Toad runs off. The foyer has two floors, and all Mirrors throughout the mansion lead back to this room.
It is also notable that if you stand under the chandelier before beating Chauncey, it will fall and you can hear Chauncey's laugh.