If you only have 24 hours to spend in Newry, some suggestions would be:
1. Visit the Narrow Water Castle - an ancient fortress with a beautiful surrounding park that you can go walking around. This might take around 1 hour.
2. Explore the Ring of Gullion landscape- an area of outstanding natural beauty with stunning views of the surrounding hills and countryside. This could take a few hours depending on how far you choose to explore.
3. Check out the Newry Canal Way - a peaceful spot for a countryside walk that can take around 2-3 hours.
4. If you're interested in history, visit Bagenal's Castle which was built in the 16th century and is now located in the center of the city. This shouldn't take more than one hour to visit.
5. Finish your day taking a stroll around the city and going shopping in The Quays Shopping Centre. This could take a few hours.