Big Fancy House/Video Games

Examples of Big Fancy Houses in Video Games include:

The Valentine Mansion, London - home to the English Countess Isabella "Ivy" Valentine from the Soul Series. The grand staircase and library are used as fighting arenas in SC 1 and SC 3 respectively.
Yai's house in the Mega Man Battle Network games—though it appears roughly the same size as her neighbors' houses from the outside.
Croft Manor in the Tomb Raider series.
A huge mansion is the backdrop of a field, the Webber Estate, in Backyard Baseball.
Wario's Castle in Wario World. It's a solid gold castle people, complete with fancy throne and lots and lots of treasure lying around just about everywhere.
- The Wario Land 2 version is just ridiculous though, it has tons of rooms, is probably the size of a small town when mapped out, and has TEN LEVELS set in the building. Getting to his alarm clock requires going through about twenty rooms for goodness sake!
The Shinra Mansion at Nibelheim in Final Fantasy VII. The largest house in the game, if this troper is not mistaken. 2 wings, 2 floors, with a deep underground basement. Get's further expanded in Crisis Core to have larger rooms, a huge entrance hall, wider corridors, and 2 levels of basements. Funnily enough, for a former scientist's base, the only room to contain anything actually scientific is the deepest, furthest room in the basement.
Phantasmagoria begins with a young couple moving into a gothic castle. It's never explained how they could possibly afford it, or why the original owner's belongings are untouched decades after his death.
Luigis Mansion. Okay, so it's a bit haunted, but you can literally vacuum money and pearls right out of the furniture!
Touhou Project's Eientei and Scarlet Devil Mansion. Both are also cases where they are Bigger on the Inside. Interestingly, the Scarlet Devil Mansion is a..well, Western-style mansion, while Eientei is very much Japanese.
Mass Effect 2: Donavan Hock has a ridiculously large house, especially after you get through the large room where the party is held, the balcony, the vault that's large enough that the Statue of Liberty's head is a display on one end, the underground security bunkers, the YMIR mechs, the garage full of tanks and fuel canisters, the secondary landing pad...and that gunship and the rest of the squadron Hock talks about had to have come from somewhere...
Fable II and Fable III have Fairfax Mansion and Bowerstone Castle respectively. Both are huge, contain any kind of real world room you could want. Both however seem to have large, rather complex escape routes that are actually filled with danger.
Dorne Manor (the Operation Repunzel level) in Medal of Honor: Frontline.
In the backstory comics for Team Fortress 2, we see that the Demoman lives in a very fancy mansion with his mother. The Heavy also seems to live in a big fancy cabin.
The Tohno mansion of Tsukihime, big and fancy even for Japanese standards.
In Battlefield 3 the Russian protagonist storms a mansion positioned on a cliff side overseeing an enormous beach spanning as far as the eye can see and a breath-taking view of the ocean. The reason why is that there is a well-known arms dealer suspected of having given away nuclear weapons so they are trying to capture him and find out what he knows. As for the mansion itself there are numerous sections one after the other that could be considered houses into their own right, lavish gardens, multiple pools, and an entire underground Military facility. This arms dealer must be banking to have been able to afford a house that beautiful.
Due to being extremely rich, Sarina's family have several of these.
The iDOLM@STER 2 - Takane's has one.
Being the head of a mafia crime family it's not surprising Jackie Estacado lives in a large mansion. What is surprising is that said mansion is located on the top of a skyscraper in New York City.
In Dragon Age II the first Act revolves around Hawke trying to gain enough money so he can reclaim the Amell Estate for his mother, after his deadbeat uncle; hid the Will that revealed everything was left to his sister, spent the entire family inheritance on himself and then finally sold the Estate to slavers in order to cover his extensive debts. After Hawke regains the family fortune and Estate in Act II, his uncle was not allowed to live there.
- While we only see a fraction of it in game, just how big is the Estate? Its vast cellars are mentioned as extending all the way from Hightown, right through to the former mine tunnels that running beneath the city, Darktown.
In Skyrim most of the houses in Solitude including Proudspire Manor which is the one the player can buy and the most expensive of the player's options. It would be big and fancy by modern standards but even moreso in the context of the setting.

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