Chantilly and Senlis
 

Plan to hit Chantilly and Senlis together by public transportation. Planning Chantilly first by metro from Paris, then bus to Senlis. I, of course, need to get back to Paris. Is it better just to reverse my trip and take the bus back to Chantilly and train to Paris, or is there a way to go from Senlis to Paris? Why I can't find it I don't know! And while I am at it, should I do Senlis, then Chantilly? Thanks.

I am not familiar with Senlis, but I can say that Chantilly might take more time than imagined. First of all, it is a good 20 minute walk from the train station to the château, and probably to the bus for Senlis. We only walked by the stables, which may be interesting of themselves, and only saw the downstairs special exhibit. Add lunch to that, and it was an entire day's outing. You might be more efficient with your time.

https://flic.kr/p/WNYkVw

The stables must not be missed, especially since the renovation of the horse museum. (I don't even have an interest in horses, but I thought it was great.) Yes, the walk from the Chantilly train station is about 20 minutes. There is a free shuttle bus, but perhaps not in all seasons or even at all since the pandemic.

Senlis made a point of being difficult to access when train lines were built and refused having a station. "We don't want to be invaded by that trash from Paris." Of course, this was more than 100 years ago.

You'll have to look up the Senlis bus schedules, but I think it is still not easy to get there.

I didn't know the metro went to Chantilly I really don't think so. I think it's a train. But you can take a bus from Senlis to Paris, it goes to the CDG airport, though. Then you can take the RER from there into Paris. This is the bus schedule
Attachment 6024

Here are the directions, it is a TER from Gare du Nord to Chantilly, or the RER D.
https://chateaudechantilly.fr/acces/

https://www.ratp.fr/en/plan-rer