Presidential Palace
The third season episode "Rumors of Death" 25 February 1980, had the following dialog:
Sula: [turns to look at Residence One] She is, after all, a tasteless megalomaniac.
Chesku: I think it's rather fine.
Sula: You would, Chesku.
Chesku: Her presidential palace.
Sula: A grotesque anachronism, like its owner. We could have built two cities for what it cost to reconstruct that absurdity.
Chesku: You keep talking like that, you'll get us both killed.
And people who read this dialog might imagine that the producers of Blake's 7 used a matte painting or a model in this episode of a vast palace equal to Nero's Golden House, or the Flavian Palace at Rome, or the Great Palace at Constantinople, or the White Palace at Ctesiphon, or the Round City at Baghdad, etc., etc.
Or maybe the producers would use a still photo or a video clip of Versailles, or the Great Kremlin Palace, or the Forbidden City at Bejing, or the Hofburg at Vienna, or some other great palace existing today.
https://en.wikipedia.org/wiki/World%27s_largest_palace
But instead they showed an English country house (a mansion with a country estate). And that mansion was not one of the largest and most famous English country houses. It was a large and impressive mansion in the neo Palladian style, but certainly not one of the largest and most impressive in that style like Houghton Hall, Holkham Hall, Kedleston Hall, Stowe, or Wentworth Woodhouse.
I didn't recognize that particular mansion as one of the great British country houses when I saw the episode, and I have never since seen a picture of a British country house and recognized it as the one from that episode.
When I was a child I lived in Philadelphia, Pennsylvania, which has an area of 142.71 square miles (369.62 square kilometers) and a 2017 population of 1,580,563, larger than the areas and populations of a few countries. And I have been to New York City.
So my idea of a city is something many times vaster and more complex than the presidential palace in "Rumors of Death", and what Sula said about the presidential place costing as much as two cities never made any sense to me. share