used to 表达过去的情况 — 英语阅读题

Read and answer. (阅读短文，回答问题) When Grandpa was a boy, he lived in a small town. There was no TV in his home, so he often played outside after school. He used to swim in the small river near his home. But now he doesn't live in the town, and he doesn't swim in the river any more. Now he swims in a big swimming pool in the city. Question: Where did Grandpa use to swim?