If you have 2-3 hours to spend in Lancaster, there are a few things you can do:
1. Visit Lancaster Castle - it's a historic castle that has been around since the 11th century and is now a popular tourist attraction. You can take a guided tour or explore the castle on your own. This will take about an hour to an hour and a half.
2. Walk along the River Lune - this is a scenic route that will take you past some of the best views in Lancaster. You can spend as long as you like on this walk, but it should take you about 30-45 minutes to walk along the river.
3. Explore the Lancaster City Museum - this museum is dedicated to the history of the city and has a collection of artifacts and exhibits that you can explore. This will take about an hour.
4. Visit the Ashton Memorial - this is a beautiful memorial building that offers stunning views of the city. You can take a guided tour or explore the memorial on your own. This will take about an hour.
5. Visit Lancaster Priory Church - it's a beautiful church that has been around since the 11th century and is a popular tourist attraction. You can take a guided tour or explore the church on your own. This will take about an hour.
Overall, there are plenty of things to do in Lancaster that can be done in 2-3 hours. You can choose to do one or more of these activities depending on your interests and the amount of time you have available.