My son loves trains. At the festival held by our shopping street, they had a working scale steam train for the kids to ride. It was his first time riding one of these alone. He managed to hold on, and to switch directions on his seat when the train came back. And he clearly loved the ride. Not bad for 2½.
(Sorry to replace the original pic. I saw a much better crop after seeing it online, then realized that I liked it better in greyscale.)
