On the contrary, it's not rude at all. I can think of little better reason to forget introductions than for admiring a city like Paris.

[ He motions generally away from the church with a smile, since as quaint as it is, it's nothing much to look at. ]

If I'm not interrupting, would you care to join me for a walk, Elizabeth? With little else to do, I'd be quite happy for a conversation partner.