The inside and outside of the abbey are based upon the mood set in the story. The mood which is a mixture between revelry and terror, is the whole purpose of the particular story. Poe seems to show how he was preoccupied with thoughts of death, and seems to show metaphorically how people know that life is futile.
The abbey inside the doesn't feel the same as the outside, since the outside is clamored with the sounds of death, meanwhile the inside is filled with the sounds of lively music, dancing, and laughter. The doors for the abbey are wielded shut, meaning no one can get out or get in. While the people suffering from the painful death from the plague, Prince Prospero is inside the abbey, laughing and dancing with his friends and knights. He seems to distract himself from what's happening outside, by simply trying to block it out with the joys of music and dancing.
The abbey is filled to the brim with all the makings of an incredible party: lots of food, jesters, dancers, musicians, and wine.Prince Prospero, the ruler of said kingdom currently being ravaged by the Red Death, is "happy" and "dauntless" and decides he doesn't want to bother with the disease. So he takes a thousand of his knights and maidens and shuts himself up with them in a hidden "castellated abbey."
The prince instructs the stranger or the "Red Death", in human form to be seized, but all of his fellow people are too frightened to seize him. So the prince decides to draw his dagger and hastily make his way