Doomsday by Warwick Deeping

At the end of October they reached Rome, and put up at the "Excelsior." They had agreed to come on to Rome because both of them had begun to suffer from concealed restlessness, and had agreed brightly and like the very best of friends that Rome attracted them. Most certainly it attracted Mary. She wanted to see it and to be able to talk about it, St. Peter's, the Vatican, the Forum, the Spanish Steps, Keats' grave, Tivoli, for she had a passion to see things, to efface her rustic insularity. The wife of Mr. Percival Fream needed to be a woman of the world.

It was in Rome that she began to discover her husband's profound ignorance. That he should have but little French and no Italian was of no moment, and quite English, and "quanto costa" carried him as far as the contents of his pocket-book, but that he should be under the impression that St. Peter's had been built by a Roman emperor was something of a shock to her. For, standing in the piazza, he had looked with his flat eyes at the mass of stone.