Jedburgh is a compact Borders town best visited as a half-day, though it earns a full day if you take the walk along Jed Water and linger at the abbey. The two key sights — Jedburgh Abbey and the Mary Queen of Scots House — are both within easy walking distance of each other and together tell the story of this corner of the Borders clearly and well.
The abbey is the headline. Enough survives to make the scale of the original building legible, and the on-site museum adds context without overwhelming. The Mary Queen of Scots House is smaller but well done, and the building itself is worth seeing regardless of your interest in Mary's biography.
Jedburgh also makes a natural base for the full Border Abbeys circuit — Kelso, Melrose, and Dryburgh are all within 20km, and each is worth a stop.