Great Smoky Mountains (at the right time of the year)

I've actually been several times, but it always seems that my timing lands in the summer. Someday I'd love to go in the fall and see all the trees changing colors.

Judging by this, the views must be incredible in real life.

And in the late spring, there are synchronous fireflies. They've become so popular that you have to get in a lottery to get access to the best locations and views. Fireflies are active throughout the summer and I loved watching them just pop randomly well into the evening, but seeing the species that actually synchronize their flashes has to be a hell of a cool sight indeed.
(I read there are 19 different firefly species in the area, each active at different hours of the day, time of year, and with unique flash patterns. Pretty cool. Where I grew up, we had some, but they were crepuscular and only came out for a brief window at dawn and dusk and then were gone. Last July, when I was in Pigeon Forge, I sat outside sipping a beer and watching Smoky Mountain fireflies actively flicker until at least 10:00, well after dark, and it was soul-soothing.)

And there is whitewater rafting, too.

I did this on the Ocoee River when I was a kid and I LOVED it, but man, the last time was probably 30, 35 years ago now. I'd love to find time to get over there and do it again (from what I hear, the river is a LOT more crowded these days, sadly (or happily, I guess, depending on your point of view)).

There are other state parks nearby, too, like Fall Creek Falls, which is another destination I saw as a kid, but have never been back to and would love to do so if I can only find the time and money to make it happen.

It's one of the rare sights I'd love to catch in the winter when it looks like this, though I suspect the timing has to be exact.