Shadowfall Manor

Shadowfall Manor is the home of the Shadow family and its various permutations across different realities.

Layout
It is a large house with two main floors and a spacious basement, with a pair of gargoyle statues perched on either side of the main front doors.

The main floor of the house consists of a kitchen, sitting room, an entry hall, and a second bathroom. Off the kitchen is the library, and off the sitting room is a doorway to the basement downstairs. The upstairs level is comprised mainly of bedrooms, with a private study.

Equestria-Only Aspects
The Equestria version of the house features, among other things, an entire secret agent facility in the basement, accessed through a doorway leading downstairs, and a second hallway filled with doors. The house was later converted into a museum following Orion's death. Visitors to the museum report seeing his ghostly self wandering the hallways and chatting to the tourists.

Human World-Only Aspects
In the human world, Gem has her bedroom on the second floor. Its color scheme consists of dark blues, dark greens, and some silvers a few shades darker than her own skin. The basement is also a home movie theater, whose main entrance door has been painted to resemble a police box.

Other Notes

 * The types of books and other knick-knacks Gem and Orion keep are remarkably consistent across all realities.
 * In a timeline briefly visited by Orion and Steno, the house was used as a military installation for the ongoing battle with an evil, god-like version of Raven.
 * In a separate timeline in which Chrysalis' invasion in "Revenge of the Changelings" was not prematurely ended by the rescued Royal Sisters, the house was heavily modified to become a smaller changeling hive. Ponyville itself became Orion's personal fiefdom after his conversion into a changeling.
 * The Equestria house was briefly visited by Gem in the story "Resurgence of the Changelings." Much was made of the similarities between the two.
 * The human world version of the house was completely mechanized in an alternate ending to the story "Cyber-Students," in which the entire population of Equestria was transformed into cybernetic humans. Charging stations were added to the kitchen since cyborgs don't require sustenance, and the bathroom became a recreation center.