In Spectre (2015), there is a meeting of the board of Spectre chaired by Blofeld. When Bond approaches the exterior it is clearly Blenheim Palace. The meeting in the interior, which features a gigantic table seating about 30 people, does not appear to be any of the rooms in Blenheim Palace. I do not think it is the Great Hall because the Great Hall and most of the rooms in the palace are built out of Coralline oolite, a type of white limestone, but in the movie the room is panelled in a green marble, so I think the interior must be from someplace else. Where?
The interior was shot on the 007 Stage at Pinewood Studios 
You can't tell movie 'stone/marble/brick/concrete' from real stone/etc until you knock on it.
It really is that good.
I've been fooled shooting exteriors where they add an extra couple of marble columns etc to partially transform a building. You don't realise until you lean on one that it's not real.
An additional hint that they might have built the interior to originally match another building, from that link...
Originally, this was supposed to have been filmed at the Palazzo Reale in Caserta, near Naples (seen as the ‘Theed Palace of Naboo’ in Star Wars Episode I: The Phantom Menace). In the end, the exterior seen in the film is that of Blenheim Palace, birthplace of Sir Winston Churchill in the village of Woodstock, Oxfordshire.
...though they could possibly have just built "any old grand hall" with no intention to match it to anything real.
Makes me think of the 'entrance to HQ' from Skyfall... which is really a car park next to Smithfield Market Google Maps 3d view & link to the Skyfall page on MovieLocations.
 The link contains the entire locations list for the movie