A tour of the bounds of Monmouthshire
The east and south
We start our tour at the very northern tip of the county, at the point where Brecknockshire, Herefordshire and Monmouthshire meet. This point is just to the south of the South Top of the Black Mountain. We leave Brecknockshire behind for the time being and head southeastwards along the Hatterrall Ridge to Hatterrall Hill. From here the boundary heads eastwards to join the River Monnow at Glandwr.
We follow the course of the Monnow as far as Rockfield Park before taking a detour around the north of the county town Monmouth to join the Wye. During the detour the boundary heads eastward through Buckholt Wood to join the Mally Brook. We leave the brook at the next tributary and head north through Pyefinch Wood before heading south again to the west of Goldsmiths Wood before crossing over the A40 to meet the Wye.
The boundary follows the Wye upstream as far as Whippington Brook, the point at which Monmouthshire and Herefordshire meet Gloucestershire. Following the brook south the boundary passes to the west of Highmeadow Woods before turning southwest at the village of Staunton. Passing to the west of Bunjups Wood the boundary rejoins the Wye at Redbrook.
We now follow the Wye downstream all the way to Chepstow where it meets the estuary of the River Severn. Following the Severn coast westbound we cross over the estuary of the River Usk and eventually meet the Rhymney river and the border with Glamorganshire.
The west and north
We now turn north and follow the Rhymney all the way to the eponymous town of Rhymney. North of Rhymney the Nant Melyn brook joins the Rhymney - the point at which Monmouthshire and Glamorganshire meet Brecknockshire. Following the brook to Dukestown, we meet the River Sirhowy which forms the border as it travels southeasterly. At the confluence of the Nant Melyn brook we head north towards Rassau until we meet the Rasa brook. This now forms the boundary in an easterly direction until its confluence with the Ebbw River in Beaufort.
We follow the Ebbw southeasterly until the tributary at Beaufort Terrace at which point we head off northeasterly towards Brynmawr. In Brynmawr the border heads easterly along Windsor Road and Bailey Street and thence passes to the south of Llanelly Hill as far as Pwll Du where it heads north along Baiden Brook to join the River Usk.
Following the Usk north we reach Gwenffrwd brook which the boundary then follows northeasterly to its source near the summit of the Sugar Loaf. From there we head north again to the Grwyne Fawr river. The boundary follows the Grwyne Fawr as it meanders northeasterly then northerly through the Black Mountains as far as the Trethiw brook. We then follow the brook northeasterly to the source close to the highest point of the county, Chwarel-y-Fan.
The boundary then follows the ridge northwards until it again heads northeastwards towards a tributary of the River Honddu. We follow the Honddu downstream until we reach the Nant-y-Ffin - the aptly-named Boundary Brook at which point the boundary heads northeastwards again back to the summit of the South Top of the Black Mountain.