Once Upon a Time Annex: Regina's Castle

I thought this was going to be a long post, but then I looked at my notes and realized that the symbolism is not complicated in this case. Regina's castle in the Enchanted Forest represents corruption. With the singular exception of Snow White, everything good that ventures into the place is destroyed.

This castle is unique and strangely modern amid the structures that make up the Enchanted Forest. I suspect that its appearance is intended to evoke Sleeping Beauty, an image of thorns and spindles and skeletal trees. Metal and glass, it is not a place that looks comfortable or inviting from the outside, or particularly at home in its environment.

The land around is inhospitable wilderness (note the water view, though).

Even the garden is severe, as regimented and skeletal as the structure itself.

Castles as a rule in OUaT represent danger and temptation. They're the standard site for weddings, but they're also the place where things go horribly wrong because people make bad choices:

1.04 The castle represents the better life Cinderella so desperately desires, and for which she makes her rash deal with Rumplestiltskin.
1.06 Contrasts the simplicity/innocence of Charming's farm life with George's castle, and his abandonment of the ideal of True Love in exchange for his mother's financial security.
1.08 The duke's castle is where he keeps the dagger that controls the Dark One, the source of his power. (I believe it's later in the series that Rumple offers to build Baelfire a castle, an offer he indignantly refuses. Rumple builds one anyway.)

Regina's castle is therefore only the most extreme and consistent example of this usage.
In Eva's day, the place looks pleasant enough on the inside.

(Are those nuns? Do they just throw in random religious elements to annoy world-builders?)
After her death and previous to Leopold's, the place is still colorful and populated if not exactly bustling.

After his death, the shift to monochrome+red is immediate.

The following significant events take place there:

1.02 - Regina murders Henry in order to cast the Dark Curse, giving in to her desire for vengeance over the protests of her own wisdom (Maleficent) and conscience (Henry).
1.07 - Regina enslaves the Huntsman after her effort to seduce him fails; as with 1.06, there is a parallel drawn, this time between the innocent violence of animals and the corrupt ways of humankind.
1.09 - Regina is bewildered and angered by Hansel and Gretel's family's refusal to abandon one another.
1.11 - Regina plays the role of the apple and seduces the genie into murdering her husband.
1.17 - Regina convinces Jefferson to get her to Wonderland, thereby tricking him into abandoning his daughter.
2.01 - Regina sends her mother to Wonderland and begins learning magic from Rumplestiltskin.
2.05 - After Victor fails to revive Daniel, Regina dedicates herself to revenge.
2.09 - Hook is recruited (kinda) into the first of a series of villainous alliances.
2.11 - Belle is imprisoned.
2.15 - Cora murders Eva.

All represented in the darkening of the silver/white interiors to black. (Note the continuity of color scheme with the Storybrooke locations, and that the predominant color there is white -- she has succeeded, with the curse, in giving herself everything that was supposed to have been Snow's.)