the seven wonders of the universe
Originally, the spacebound Orient Express in 'Mummy On The..' was scheduled to visit The Seven Wonders Of The Universe. Indeed, in the first few drafts, she did just that, with passengers getting off to explore exotic ruins as they discussed the mysterious deaths plaguing the train.
However, the pressures of fitting everything into 45 mins caused the Wonders to all be stripped away. The smallest echo of this premise still remains in the set design, in the form of this sign, which I liberated from a corridor set as it was being destroyed.
You can catch a glimpse of this sign as Clara follows Maisie when she's carrying her shoe and it's also on a table in The Doctor Who Extra for the episode.