The bony labyrinth (also osseous labyrinth or otic capsule) is the rigid, bony outer wall of the inner ear.
The bony labyrinth is enclosed inside the petrous bone and can be divided in three parts: the semicircular canals, the vestibule and the cochlea.
These are cavities hollowed out of the substance of the bone, and lined by periosteum. They contain a clear fluid, the perilymph, in which the membranous labyrinth is situated.
Moreover, the meatal, labyrinthine, tympanic and mastoid segments of the facial nerve cross these regions.
These structures of the inner ear and the internal auditory meatus mark the anatomic barrier between the anterior petrous bone or petrous apex, and the posterior petrous bone where the mastoid antrum and cells lie.