If you want to play tennis, I know there are two places. One is Liang Zhong, which is a charging place, and no one is there. The place where the venue is empty all the year round is the Teachers College. People don't often play, but there is no charge, but sometimes the gate of the tennis court is open! It's open most of the time!
In addition, I heard that there is also a tennis court in a certain district of Lishan, but it is charged. I heard it's been open for a while, but I don't know if it can be opened now!