as you can see

Yes, you just know Irene Ryan is going to pop out of that trunk.

The 1920s renovation included the curved staircase. From the 1982 application for inclusion on the National Registry of Historic Places Inventory:

The interior reflects the 1920s remodeling in such details as the central spiral stair and Georgian Revival woodwork. ... Since the 1920s renovation, the focal point of the interior has been the flying spiral staircase at the center of the house at the intersection of the hallways. The staircase is decorated with a wrought-iron handrail carried by two slender balusters per tread.

Mirador was the childhood home of Nancy Langhorne (later Lady Astor, the first woman member of the British Parliament and opponent of Winston Churchill), as well as her older sister Irene, who married Charles Dana Gibson and was the model for the Gibson Girl. The Adams renovations occurred during the ownership of Nancy and Ronald Tree -- Nancy Tree was Nancy Astor's niece.

Also reminded me of the Clampett Mansion. Through the arched doorway look at the giant spool of thread turned on the side.

I love the compass rose on the floor.

As a stair and handrail craftsman of the last 30 years, I find the simplicity of this design very graceful. There was a lot of work that went into its construction. The interior framework of the structure could be made of iron or steam-bent wooden stringers. The newel post and balusters look as though they are made of iron. Mainly because their slim design would be very flimsy if made of wood. The handrail itself looks to be steam-bent wood. The volute at the bottom end of the handrail was surely carved out of a block of wood. The large wood starting tread at the bottom is very inviting. The curved bottom riser was a tricky piece to make. The skirtboards along the wall could be plaster, but are more likely bent wood. All in all a simply and gracefully beautiful staircase.

Curved stairs certainly are impressive feats, but they aren't necessarily as difficult to design and construct as you may think. In many cases there will be several beams or joists cantilevered from the wall to support short sections of the stair. That way the outer beam doesn't have to be a single long serpentine affair. Even so, it would usually be a laminated beam glued up from smaller pieces that are easier to bend into such a compound curve.

Just a small country home with a nice view.

The curves give this an elegant modern look. Although at first glance, I too thought it was a "Beverly Hillbillies" soundstage shot of the Clampett home.

That's one impressive staircase. Imagine the design, carpentry and finishing skills required to construct a free-flying staircase with such a long complex curve. Even if added as part of the "1920's renovation" it's impressive. How would YOU design the beam that supports the outside edge?

Of the Clampett Mansion staircase.