I thought there was another thread for this topic already, but I can't find it yet. This is one way I'd see the interior of the palace of Charn but ruined of course. Apart from Pauline Bayne's illustrations, that is. Both of these pictures are of the Assyrian civilisation of Nineveh. The 1st is of the city. But the second is of one of the halls in Sennacherib's palace. The back wall beyond the winged lions with human heads looks very much like a hall of images. 

I had previously posted a similar but different question - mine was specifically about how people imagine Charn when they read the books (not how they would necessarily depict it for a movie).

C S Lewis describes the palace in which the Digory and Polly arrive as being full of large courtyards, high walls and arches.  I associate courtyards with Medieval Castles and Universities, so my mind naturally goes in that direction.  Likewise, the mention of dungeons and torture-chambers leads my mind in a medieval direction (even though these descriptions don’t necessarily say ’medieval’ explicitly.

The walls rose very high all round that courtyard. They had many great windows in them, windows without glass, through which you saw nothing but black darkness. Lower down there were great pillared arches, yawning blackly like the mouths of railway tunnels. It was rather cold.

The stone of which everything was built seemed to be red, but that might only be because of the curious light. It was obviously very old. Many of the flat stones that paved the courtyard had cracks across them. None of them fitted closely together and the sharp corners were all worn off. One of the arched doorways was half filled up with rubble.

…

“That doesn’t look very safe,” said Polly, pointing at a place where the wall bulged outward and looked as if it were ready to fall over into the courtyard. In one place a pillar was missing between two arches and the bit that came down to where the top of the pillar ought to have been hung there with nothing to support it. Clearly, the place had been deserted for hundreds, perhaps thousands, of years.

…

The Queen led them out of the Hall of Images into a long corridor and then through a whole maze of halls and stairs and courtyards. Again and again they heard parts of the great palace collapsing, sometimes quite close to them. Once a huge arch came thundering down only a moment after they had passed through it.

…

“That is the door to the dungeons,” she would say, or “That passage leads to the principal torture chambers,” or “This was the old banqueting hall where my great-grandfather bade seven hundred nobles to a feast and killed them all before they had drunk their fill.

…

And on the earth, in every direction, as far as the eye could reach, there spread a vast city in which there was no living thing to be seen. And all the temples, towers, palaces, pyramids and bridges cast long, disastrous-looking shadows in the light of that withered sun. Once a great river had flowed through the city, but the water had long since vanished, and there was now only a wide ditch of gray dust.

From all this, I think Charn should look somewhat familiar (it could be other-worldly, but we should be still able to recognize the buildings from equivalents in our world).  I think I  would lean heavily into the ancient world vibe (though I love the idea of portraying a modern city, but with stone skyscrapers rather than metallic and glass skyscrapers).

Given that there are no living things (which presumably includes bacteria and microbes in general), it should not look like an overgrown ruin.  I.e. While the ruins in “Dawn of the Planet of the Apes” looked amazing, Charn cannot have trees and ivy growing over the ruins.

References that could be useful could include Ancient desert ruins (as these usually don’t have intruding plant life).  (None of these cities are big enough, but they show ruined rock structures without plants):

Ziggurat of Ur

City of Ur - where Abram lived

City of Ur 2

City of Uruk

Ancient Desert Ruins

Sahara Desert ruins

Gobi desert ruins

Ancient Egyptian Temple

Ancient desert ruins

Desert ruins

Saudi Arabia ruins

Badi Palace Ruins

Ancient corridor ruins

Ancient corridor with windows

Syrian Ruins

Something a bit different would be to use underwater ancient ruins as reference (just because they have a different characteristic – I used to wonder what a city like New York would look like if it was completely submerged beneath water)

Underwater ruins

Underwater ruins 2

Underwater ruins 3

Underwater Mayan Ruins

Underwater Samabaj Ruins

Underwater Samabaj ruins 2

Underwater ruins 4

Underwater Rome ruins

Underwater Lake Titcaca ruins

Architecturally, I imagine it something like these though (minus any plants):

A courtyard

Another courtyard

Technically, I would love it if they used miniatures / models for the city rather than relying on CGI (think the bigatures from the Lord of the Rings movies).

@davidd  ...large courtyards, high walls and arches.  I associate courtyards with Medieval Castles and Universities, so my mind naturally goes in that direction

Of all the links you have shown in your post, I like the Badi link, and the two ancient corridor pictures most. I am a bit dubious over the Ur links or even the Saudi Arabia & Gobi ruins, when the Nineveh palace one didn't show arches, unlike these two of the actual ruins at Nineveh, which I've shown below, when that civilization was cast down after the 605 or 606 Battle of Carchemish, to be replaced by Nebuchadnezzar's Babylon. Both these two civilizations were noted, in the Bible for their cruel treatment of prisoners, such as Hezekiah's son, Manasseh & Zedekiah, at the end of 2 Chronicles. Especially the Assyrians, though their Australian descendants & their modern-day writers have commented that this might have been an exaggeration to strike terror in neighbouring people, like the people of Samaria (Israel & Judah) plus around Tyre, Sidon & Byblos, called the Phoenicians by the Greeks because of the purple dye they traded. 

The reason why those desert ruins and those of Ur might not fit the bill is because they don't show arches, therefore we don't know whether or not those civilizations knew how to make them. The courtyards are a different matter, and are distinctive features of most palaces such as Beijing's Forbidden City or Istanbul's Topkapi Palace which I have shown you as well. There is also a central courtyard even in Scotland's ruined Linlithgow Palace, as well.  

Nineveh ruins with arches                                                          

Topkapi Palace looking towards Istanbul, but it isn't a ruin.     

I would’ve picture Charn to be something similar to Assyria or even any of the ancient civilizations.

For film, I think the scene with Charn could be a good opportunity for sound design. So perhaps when Digory and Polly arrive, a hint of something, an unfamiliar place and environment, where there’s no sound or movement, totally different than our world. It could be a very unsettling moment. So a good opportunity for sound design as well.

Or how about Vulcan on Star Trek?  Wouldn’t Charn be something like that planet?  “If the heat doesn’t get you the thin air will”, I remember Dr. McCoy saying. Of course I wouldn’t expect the inhabitants to have pointed ears.  But I remember the landscape was rather dry and had a lot of ancient ruins, which was similar to Charn. You wouldn’t expect much greenery on a world like that. 🙂

@narnian78  Maybe you are right about Charn being somewhat extraterrestrial. But we see it in the blighted light of a dying sun, and though it might be just as ruined as Nineveh ever since the 605 BCE battle of Carchemish, or even the all too latest-news modern-day Gaza city, the beginning of which precedes even ancient Nineveh, dating from about 1500 BC, according to Internet. The point of Charn is that dead, still, desiccated and devoid of vegetation as it might be when Polly & Digory arrived, is that people did at one time live there, nonetheless, cruel, sinful & unhappily, as they might have been. Apart from Jadis, herself, all life had gone. 

@davidd Technically, I would love it if they used miniatures / models for the city rather than relying on CGI (think the bigatures from the Lord of the Rings movies).

Now you are talking. That well might be a more economical & effective way to re-create Charn, or at least the most relevant bits, I should think. And the LOTR ambience wouldn't be out of place, either. Remember Barad-Dur? Or Minas Morgul? Of course, currently Prime is still in the throes of producing Season 3 of Lord of the Rings: Power of the Rings. So, then a bit of creativity is needed to distance MN from that production. 

I mentioned Beijing's Forbidden City, the one-time Imperial Palace, there, with its spectacularly broad steps leading up to the terrace outside Charn's royal palace. I could well imagine something similar for Jadis' sister to walk up, her troops behind her, if that scene is to be depicted at all. I've seen something even more spectacular in Mayan ruins I think it was, entering into some pyramid or other. But not underwater, & somewhat bigger, like your image from Underwater Mayan Ruins.