Mansion of Many Apartments is John Keats's image for the mind's capacity to move through different stages of thinking and imagination. He compared early, simple awareness to the first rooms of a large house and deeper, more reflective understanding to later chambers. Keats used the metaphor to describe intellectual growth, especially the move from ordinary perception to richer, more mature thought.
Example
At first she sees only the bright window of the scene, but as the poem deepens, her mind passes into the mansion of many apartments and begins to question what lies beneath the surface.