Travelling north across the border from England on the A74 the first place of any size you will reach is Lockerbie. While historically the name now has some tragic connotations, it is actually a pretty wee place, surrounded by beautiful countryside, and, of course, it is so accessible.
It is easily accessible and ideal as a base from which to explore the area round about. From there it is easy to head north into the Border hills which offer great walking, while rivers such as the Nith provide equally excellent fishing. To the west, the Solway coast, with some wonderful sandy beaches, is within easy driving distance, as are Drumlanrig Tower and country park or the Samye Ling Tibetan Centre. Up the motorway, Leadhills and Wanlockhead are well worth a visit, and, given the good roads, both Edinburgh and Glasgow are both feasible for day trips.