Twin Ring Motegi is a motor racing track in Tochigi. There are a number of racetracks there. There is a Formula-1 type track, a regular race car track, a dirt track and a go cart track. There are lots of driving courses like safety training (of course, this is Japan), riding in a stock car at high speeds, driving a big yellow USA school bus and more.
I wasn't expecting to enjoy our trip there very much. We are not into motor sports at all. Anyway we ended up going with some folks from work and had a good day. If you are in the area then I think there are a couple of things your shouldn't miss there.
First of all is the Honda Fan Fun Lab. It shows some Honda future technologies. Its not that big and won't take you that long to walk around it. But there is an outstanding display of the history of Honda robots. And there is a demonstration where you can watch their latest robot walk around on stage.
Next there is the Honda Collection Hall which has a very large display on the history of Honda motorcycles, cars and race vehicles. Its really very good too. The best vehicle is an old wood and bronze steam motorcycle.
All in all a pretty good day. I recommend the trip. Especially if you are in the area. It would combine well on a day trip with the Mashiko pottery area which is also nearby.