Here we are on the final part of the journey southwards and there is a choice to be made in Rhaeadr. Follow the A470 along the banks of the River Wye or turn left and follow the A44 to the town of Llandrindod - with its Victorian buildings and wells - and onward on the A483 to join the A470 at the roundabout outside the Royal Welsh Showground at Llanelwedd. For a week every July this area is very busy and, if you are in a hurry to travel between south and north, you'd better travel along an alternative route!

On past the Little Chef and cross the bridge over the River Wye and we've arrived in Builth Wells. There was a Norman castle here but nothing remains today. In this area - about three miles westward on the A483 in the village of Cilmeri - Llywelyn ap Gruffydd (Llywelyn the Last) was killed in 1282 as he was fleeing from the English. The town grew in the 19th century when people came here to enjoy the spa waters.

The A470 leaves Builth and follows the River Wye down to the village of Llyswen. Here the river turns back north-east for Hay on Wye - the town known for its bookshops and literature festival - before crossing the border into England. But we travel southward through an area which was important in Welsh history. About a mile from the village of Bronllys, on the A479, lies Talgarth and here, by the church, is the grave of Howel Harris, one of the fathers of Methodism in Wales.

Ahead of us now are mountain ranges - the Black Mountains to the south-east and the Brecon Beacons to the south - and in the distance lies Pen y Fan, the highest peak in the South. The A470 takes us towards Brecon. On the roundabout where the A470 meets the A40, there is a choice to be made - take the fast dual carriageway past Brecon or take a detour to see this old town on the banks of the rivers Honddu and Usk. This lovely town is a centre for visitors to the Brecon Beacons National Park and every August the streets are full of the "hwyl" and sounds of the Brecon Jazz Festival.

The other side of Brecon the A470 goes westward - to Llandovery, Llandeilo and Carmarthen - but the A470 turns south and in to the mountains. The road climbs up the valley of the river Tarell till it reaches the Storey Arms outdoor centre. This is the place to look back over the Tarell Valley, the Usk Valley and the Epynt mountain range in the distance. To the west lies the side of Y Fan Fawr and to the east is Pen y Fan. Ahead lies the valley of the River Taff; so, down we go.

From Storey Arms the road descends past three reservoirs till it reaches Merthyr Tydfil. (The name means the Grave of Tudful, one of the daughters of King Brychan Brycheiniog.) The town grew around a number of coal and iron villages, such as Penydarren, Pentre-bach, Cyfarthfa and Dowlais; by 1801, Merthyr was Wales' biggest town. The place is famous for Dic Penderyn and the Merthyr Riots, Richard Trevithick and the first steam train, and Joseph Parry - the man who wrote "Myfanwy".

Today, the A470 bypasses Merthyr and the small villages at the top of the valley - place like Aberfan, where a coal tip slid on top of the village school in 1966 and killed 126 children and 26 adults. Onward we go and down to the big roundabout where the River Cynon meets the Taff; here the A4059 goes up the valley through places like Abercynon, Mountain Ash and Aberdare. But we continue on the dual carriageway to the town of Pontypridd. This is where the River Rhondda meets the Taff and in Ynys Angharad Park lies the memorial to Evan and James James, the father and son who composed "Hen Wlad fy Nhadau".

Onwards once more. Past the junction for Caerphilly and its famous castle until we reach the outskirts of Cardiff and Castell Coch castle up on the hill on the left. On, under the M4 and we must slow down now because there are police cameras and traffic lights all the way to the city centre! We're now travelling through the suburbs of Whitchurch and Birchgrove and on to the city centre.

On through the Civic Centre and its beautiful buildings - such as City Hall and the National Museum. On past the busy shopping centre of Queen Street and past Cardiff Castle. Then, turn down St Mary Street, under the railway bridge, through the traffic lights and along Lloyd George Avenue till we reach the National Assembly and Cardiff Bay - an area of new buildings on the waterfront.

And that's the end of the road between North and South for the A470 - about 200 miles and four hours of non-stop travelling. This is an important road which connects the Capital with Mid and North Wales. Perhaps, one day, there will be a dual carriageway all the way to bring Wales's people closer together!