This Sunday, I attended the Dupont Circle house tour. Included in the stops was one of my favorite house museums -definitely my #1 in DC. The Anderson House was completed in 1905 and is a great example of the gilded age right here in DC. Currently, the building houses the Society of the Cincinnati since 1937and is operated as a house museum as well.
The approach to this house is what I love most about it. While on a busy city street, just 2 blocks from Dupont Circle, you would think you were in a quiet suburb. The house fronts the street, but has a walled entry courtyard which blocks most of the noise. It hasn't been changed (the upkeep on this house is AMAZING) and it still has beautiful and environmentally friendly gravel which does a lot to muffle any street noise. 
This is a huge 50 room mansion but the scale may not convey that. Look how tall these entry portals are! The house was designed by the Boston architects Arthur Little and Herbert Browne in the Beaux-arts style as the winter home of Larz Anderson III and his wife Isabel. Anderson was a diplomat to many countries, including Japan in 1912 and the house is filled with remnants of his time there. 
The house is what you would expect: breathtaking! There are both English and Italian influences, as well as many parts and pieces of European palaces and cathedrals (including an entire choir stall in a small room off the entry). Every room is ornate featuring carved wood walls, murals, gilded ceilings, ornate iron work and intricate marble and wood floors.
The approach into the house belies its size, another thing I like about it. You enter into a small hallway, you can turn left to a small staircase up to the gallery, or to the right you go through a small room filed with a choirstall from a cathedral and into the main stairhall with amazing trompe l'oeil wall paneling. This large painting from 1911 dominates the top of the stair landing - placed there to seem as if the procession of women is about to come down the stairs.
On the other side of the stairhall is entry into the ballroom and into the wood paneled billiard room (now houses rotating displays, currently treasures from their library). The ballroom is magnificent, as one would expect. Above on the minstrel's gallery is a beautiful (and huge!) portrait of the Andersons seen below.
I couldn't find any pictures, but off through the french doors on the right is the orangerie and breakfast room overlooking the large terraced back yard. White walls with green trellis work, marble columns and floors, ceiling painted as the sky and other garden murals - really charming -what a great place for breakfast! Elsie de Wolfe would approve!
This shot reflects how the light pours into the room through the orangerie, trees and chandeliers. It is a dramaticly lit space!
And you can rent it for parties, as seen above. At the top of the mainstaircase is this landing below with intricate marble herringbone floor and beautiful tapestries. You can go into the 2nd floor gallery seen here, or into 2 beautiful french salons -all gold and white 18th century France.
The gallery houses many items in display cases as well as a majestic view over Massachuestts Avenue and the beautiful Cosmos Club across the street (my #1 place I need to get into at some point in dc!, anyone have connections?). 
The dining room has more tapestries and is pretty massive. What a place to have dinner! Attached through a double padded doorway is the beautiful corner butler's pantry with tons of windows - grand placement for such a service space. Of course I was in heaven surrounded by beautiful antique china!
This is the 2nd salon below, behind the french one I mentioned. It's actually a pretty long walk from the dining room to this room for after-dinner conversation; All the better to view the owner's collections I imagine!
I found this image of the home in the 1940s - you can see it hasn't changed much. Now to the left is a very large opulent hotel and a mid century apartment building to the right -both dwarfing the mansion and built RIGHT up to the walls!
I'll end here with some night views. As pictures are discouraged on the housetour, I was good and didn't take any. All of these are courtesy of flickr. If you're ever in DC, make sure to visit the home -tours are free and operate Tuesday through Saturday from 1 till 4, I believe. The house is located at 2118 Massachusetts Ave, NW, along embassy row - about 2 blocks from the dupont metro. You can read more about it at their website 
