If you have 6 hours or a half day to spend in Caerleon, here are some suggestions:
1. Visit the Roman Amphitheatre: This is the most iconic attraction of Caerleon. It will take around 1-2 hours to visit and explore the ruins of this amphitheatre.
2. Caerleon Roman Fortress and Baths: A great place to learn about the Roman occupation of Wales. It will take around 2-3 hours to explore all the exhibits and buildings.
3. National Roman Legion Museum: This museum provides an in-depth look at the life of the Roman soldiers. It will take around 1-2 hours to see all the exhibits.
4. Caerleon Arts and Crafts Centre: Shop for some unique souvenirs or gifts made by local artists. It will take around 30 minutes to 1 hour depending on how much shopping you do.
5. Walk along the River Usk: Enjoy a leisurely walk with beautiful views of the river and the surrounding area. It will take as much time as you want.
Overall, you can plan your itinerary based on your interests and the amount of time you want to spend at each attraction. Don't forget to try some local food and refreshments in the many cafes, pubs and restaurants scattered throughout the town.