What is a hobby you enjoy, but seems too quirky or obscure to bring up in most conversations?

In addition to general learning which might be my favourite, I have multiple.

Maybe the most niche is a historical reenactment and historical costuming. Latter usually based on extant garments or garment finds. I try to get as close to the original in techniques, tools and materials using the best evidence I can find.

I also plan things that will never happen. I decorate houses and apartments on paper. I make extensive plans for travel that I can never afford unless I win in Lottory. Which I even never play.

I spend absolutely too much time playing with spreadsheets.