Well, you asked for it...
You can click all of these thumbnails for full versions...
Top level/above ground (left) | Bottom level/under ground (right):
The exterior would be similar to Rosecliff (but one floor):
The grand staircase prominent in the top level would be like Buckingham palace:
The decor would be similar to this, albeit a bit darker red:
And like this:
The yard would have an italian garden in similar style to this:
Though, the plants themselves would be different. In fact, they'd mostly be fake plants that just look really good and all of the perfectly manicured grass would actually be fake grass so I wouldn't have to maintain it or pay for it to be maintained.
And here's some various things I'd have stuff in similar style to:
I'd probably have a lot of statues 3d printed myself that I'd make in DAZ Studio, like have the bases 3d printed then just fill them with cement and then I could sell copies of them to recoop the costs of having them 3d printed.
A lot of the fancy gold work around the house I'd actually have 3d printed as well but I wouldn't want it to be gold because that's way too expensive. I'm thinking some kind of anondized polished brass or some kind of non-tarnishing metal that could look like polished gold and not tarnish but be very cheap.
The house itself would be built almost entirely as an insulated reinforced concrete shell which would make it tornado proof, which is also why the living areas are underground since you would be safe. The home being reinforced concrete also prevents the possibility of something like a house fire since concrete doesn't burn. The heating/cooling system would be cheaper and ran through the walls since it's much cheaper to heat/cool a reinforced concrete home. It'd be great because the concrete could be molded to the shape I want the exterior to be and after being treated it'd look like it'd been clad in white terracotta tiles.
The underground garage would open up from the front of the driveway in front of the fountain. You could drive over it without even noticing that it was there but with the right gate opener it'd open up and you'd drive down a ramp and down into a great garage.
The house would be built earthquake proof as well with a foundation intended to be able to sway several feet if needed, so it'd be pretty good against natural disasters of all kinds.
I was also thinking about having the pool so it looks similar to Queen Sophie Anne's pool from True Blood in that there'd be false walls with decor/lights that make it look like it's above ground and that it's a beautiful day outside. Like so:
The house isn't actually as huge as it looks, it's actually just slightly larger than an average house, certainly not palace sized. It's designed with four master bedrooms and master baths just so whoever ends up living in it would have great accommodations. It'd leave room for self+spouse and the possibility of something like 3 kids, or 6 kids if you put 2 per room (but holy hell I'd never have 6 kids, even 1 would be pushing it). Aside from kids it could also be used for something like a maid or something, if I ever had that kind of money to afford one. But the house is designed to be pretty affordable so despite looking extremely fancy I wouldn't necessarily be rich to be living in it.
You can find a lot of info on how the house would be built here since it outlines a lot about building concrete reinforced shells: http://www.tornadoproofhouses.com/