Actually good timing as I am pondering the same exact question right now.
I want to treat my father, who is slowing down quite a bit this past year, on another good international trip in early Fall (sadly probably the last time he’ll be able to make a really long flight).
In December 2019, I had mapped out a ride for us that summer (2020) on the Trans-Siberian Express from Beijing to Moscow and my father (who never traveled much until I started taking him on trips) was all-in on letting me take him on what would probably be the most random adventures of our lives.
As you know, that part of the World has had a lot more challenges since Spring 2020 than worrying about two Americans Tourists who wanted to sight see on a train.
I thought about the Paris Olympics (because it is Paris and some event tickets are surprisingly very reasonable right now) but it doesn’t seem that element of “we are not exactly sure what we are getting into” that we had on a couple of the other trips I took him overseas.
He loves learning about WW2 history from our family’s WW2 military service. There is a Guide, with very mixed reviews (which I think gives that twist of what are we in for), that does private WW2 Pacific Island Hopping Tours of Guadalcanal, Peleliu, etc.
I am going to email the Guide for his availability and see how we can get on his schedule (if available) and then end up at the Park Hyatt in Tokyo where I have been selfishly wanting to take the “Lost In Translation” Movie Complete Places and Sets Tour for $199.
Anyways, sorry I got off topic.