The essence of a museum is arguably its physical location and its tangible collections. You may see with your own eyes, for example, the full original of a painting you have only dimly glimpsed in black-and-white in an art textbook, or marvel at ancient artifacts from vanished civilizations.
However, we are also interested in literary museums, those that consist only of words and whose construction is unencumbered by the laws of physics.
Italo Calvino's Invisible Cities imagines Marco Polo spinning tales for Kublai Khan about the metaphysical communities that he has encountered in his travels around the Kublai's vast empire.
One of these cities has a museum and here is its story:
CITIES & DESIRE 4
In the centre of Fedora, that grey stone metropolis, stands a metal building with a crystal globe in every room. Looking into each globe, you see a blue city, the model of a different Fedora. These are the forms the city could have taken if, for one reason or another, it had not become what we see today. In every age someone, looking at Fedora as it was, imagined a way of making it the ideal city, but while he constructed his miniature model, Fedora was already no longer the same as before, and what had until yesterday a possible future became only a toy in a glass globe.
The building with the globes is now Fedora's museum: every inhabitant visits it, chooses the city that corresponds to his desires, contemplates it, imagining his reflection in the medusa pond that would have collected the waters of the canal (if it had not been dried up), the view from the high canopied box along the avenue reserved for elephants (now banished from the city), the fun of sliding down the spiral, twisting minaret (which never found a pedestal from which to rise).
On the map of your empire, O Great Khan, there must be room both for the big, stone Fedora and the little Fedoras in glass globes. Not because they are all equally real, but because all are only assumptions. The one contains what is accepted as necessary when it is not yet so; the others, what is imagined as possible and, a moment later, is possible no longer.
Italo Calvino, Invisible Cities, 1972; translated by William Weaver