If you only have 24 hours to spend in Barnard Castle, here are some suggestions:
1. Visit the Bowes Museum - this museum has an impressive collection of fine and decorative arts, including works by famous artists such as Turner and Canaletto. Plan for at least 2 hours here.
2. Hike up to the castle ruins - take a walk up to the ruins of the castle, which offers great views of the town and Teesdale. It should take around 1 hour to hike up and down.
3. Explore the town centre - the town centre is full of charming independent shops, cafes, and restaurants. Spend some time browsing and grabbing a bite to eat. Plan for at least 2 hours here.
4. Walk along the Teesdale Way - explore the picturesque Teesdale scenery on foot by walking along the Teesdale Way. This could take anywhere from 1-3 hours depending on how far you go.
5. Visit Egglestone Abbey - this 12th-century abbey is located just outside of Barnard Castle and can be reached by foot or car. Plan for around 1-2 hours here.
Overall, you can easily fill a day in Barnard Castle with these sights and activities. If you have any extra time, consider checking out the local markets or taking a stroll along the River Tees.