What was unusual about the images Lord Azriel show the council meeting

Lord Asriel showed images of a city in a far away place. The place is called the Aurora (Northern Lights), and there seems to be an expedtion other than Lord Asriel's present. He also brought the scholars the head of Stanislaus Grumman, who'd been murdered.

She pressed her face to the crack to see more clearly, and she could see the Scholars near the screen leaning forward too. As she gazed, her wonder grew, because there in the sky was the unmistakable outline of a city: towers, domes, walls...Buildings and streets, suspended in the air! She nearly gasped with wonder. The Cassington Scholar said, “That looks like...a city.” “Exactly so,” said Lord Asriel. “A city in another world, no doubt?” said the Dean, with contempt in his voice.