If you have 2-3 hours to spend in Three Rivers, here are some suggestions:
1) Visit the Aquadrome - This is a beautiful park with lakes, nature trails, and recreational activities. You can rent a bike or boat, take a walk or grab a bite to eat at the onsite cafe. Time needed: 1-2 hours.
2) Explore the Rickmansworth Canal - Take a stroll along the canal and enjoy the scenic views. There are several pubs along the way where you can stop for a drink or a bite to eat. Time needed: 1 hour.
3) Visit the High Street - Three Rivers' High Street is a charming place with several shopping and dining options. You can browse the shops and grab a coffee or a meal at one of the cafes or restaurants. Time needed: 1-2 hours.
Overall, there are several things you can do in Three Rivers within 2-3 hours. Pick one or more activities based on your interests, and make the most of your time in this charming town.