THIS week's Diary comes from Hereford, which is close to the Welsh border. It is a small but delightful city containing a wealth of history in its setting among lush and beautiful countryside. It is a former Saxon capital of West Mercia and remains a focal point for the social life of Herefordshire in addition to being a busy commercial and administrative centre.

In many ways, it reminds me of York and Durham. It is dominated by a splendid cathedral which stands near a very compact city centre; the city is divided by a river (the Wye) and it was formerly a walled town, remnants of which remain. The city centre is rich with shops, churches and offices and there is a bewildering network of narrow streets and alleys; there is a busy railway station too!

Beyond doubt, the centrepiece is the Cathedral Church of St Mary the Virgin and St Ethelbert the King, not only because of its long history and impressive structure, but also because it houses the world-famous Mappa Mundi and the equally famous Chained Library of some 1,500 priceless volumes.

A cathedral on this site served the diocese as early as AD676, but a stone one was built shortly before the Norman Conquest, then destroyed by Welsh invaders in 1055. The Normans began to rebuild the cathedral in the latter part of that same century and over the years it has been subjected to many attacks, changes, additions and improvements.

To give a few examples of its treasures, the north door dates from 1300, the roof of St John's Walk which leads from the cathedral to the college cloisters was installed in 1470. The font's age is unknown, but it is probably the oldest artefact in the place. Like so many other aspects of this church, images of the apostles on the font were defaced during the Reformation - this fine old church bears many such scars as the Roman Catholic church of the time was ousted in favour of the new Protestant religion. A later disaster occurred on Easter Monday 1786 when the nave and the tower collapsed, this providing the necessary impetus for the cathedral to be restored.

Pride of place must go to the unique Mappa Mundi and the Chained Library, both housed in the specially-built New Library Building funded by a generous gift from Sir Paul Getty and opened in 1996. The Mappa Mundi (Map of the World) is one of the most remarkable and important medieval works of art in existence; it is the largest and best surviving example of a particular type of cartography which flourished in this country during the twelfth and thirteenth centuries.

The map purports to show the world as it was thought to be around 1280, the centre being Jerusalem with continents, countries, mountains, seas, rivers and towns being shown in what we would consider highly unlikely settings. The Garden of Eden is shown, for example, along with pictures of Adam and Eve eating the forbidden fruit and there are some 500 drawings on the map, some depicting animals both real and imagined, with some curious ones from mythology, buildings like the Tower of Babel, and biblical events such as the Exodus from Egypt and Moses receiving the Ten Commandments on Mount Sinai.

Words cannot do justice to this unique map which is 5ft 2in high (1.58m) and 4ft 4in wide (1.33m) on a single piece of parchment or vellum; one must see it for oneself. It is kept in an environmentally controlled case in a secure room, although there are many reproductions both large and small - and England is shown along with some of its more important cities. So who compiled this masterpiece? It is signed by Richard of Haldingham or Lafford (Holdingham or Sleaford in Lincolnshire) but nothing else is known about him. It is thought the map originated in Lincolnshire and it was brought to Hereford at a later date.

Hereford's Chained Library is also unique. The huge bookcases and strong chains in which the volumes are kept date from the seventeenth century, although some of the rare books date from as early as the eighth century and the more modern ones are as recent as the nineteenth century. This wide range of dates shows impressive continuity, for there has been a working theological library in Hereford Cathedral since the twelfth century.

So why chain books to a bookcase? The simple answer is that it was to prevent them being stolen. Books were once considered to be of immense value, in some instances being worth more than a farm or a house and so their owners chained them to a bookcase. The chains allowed them to be placed on a sloping desk from where they could be studied. Today, the Chained Library in Hereford contains some wonderful old volumes, the earliest being the Hereford Gospels, which date from the eighth century. This book of four gospels (Matthew, Mark, Luke and John) was given to the cathedral by Athelstan who was bishop of Hereford from 1012 to 1056.

The countryside around Hereford is lush, beautiful, peaceful and inviting, yet it is not regarded as a tourist honeypot. Indeed, as we motored around the lanes, well off the main routes, there were times we were the only car on the road. It gave us time to admire the scenery and explore tiny villages for this is apple growing country as well as the home of the familiar white-faced Hereford cattle.

The world's largest cider producing factory is in Hereford (there's a cider museum, too) and the ground, with its distinctive reddish soil, is highly fertile. Gardens and farms benefit from this, and the home-made food we sampled (and there was lots of it) was scrumptious.

Down one narrow lane, wide enough for only a single vehicle, we found a garden beside a sorry-looking mansion; the garden was open to the public and so we went in to find a tiny cafe full of home-made bread, cakes and cider, and an expansive park-type garden created from fields and river-side woodland. It was run by an elderly woman who did all the work herself and so we toured her wonderful garden (it was wonderful by any standards) and bought a few plants in the hope they would survive in our northern earth. I am amazed that just one person could cope with such a large and imaginative piece of cultivation, but it seems the woman is a legend in the district. She deserves to be.

The lushness of the district can be gauged by the fact we were in the Golden Valley. One of the features is Abbey Dore, this being a stunning parish church built from the remains of a former Cistercian abbey. The name is interesting - D'or comes from the French, meaning "of gold," and this makes me wonder whether the Golden Valley's name is from that source.

The nearby river is also called the Dore and there is a suggestion that the name really comes from the Welsh dwr meaning water, the Norman invaders mistaking the pronunciation as their word d'or.

From there we explored yet more lanes and found ourselves in an even more amazing place - Kilpeck. This tiny village, tucked among the hills, boasts one of the finest surviving Norman churches in Britain. Its exterior is covered with elaborate stone carvings, which are an astonishing mixture of Celtic pagan images and those from the early days of Christianity. It is thought the church was built around 1140 and although it is constructed of sandstone, these gargoyles and images have survived the weather for more than 850 years. The south door is astonishing, with its images of snakes, the green man, signs of the zodiac, an imaginary beast called a mantichore, a basilisk (born from a cockerel's egg) and warrior soldiers. This tiny church has intrigued scholars down the centuries and continues to captivate on its hilltop site.

We found a couple of castles nearby, too, both inside the Welsh boundary and both open to the public at no charge. One was at Grosmont, a hilltop border village which has its namesake in North Yorkshire's Eskdale, and the other at Skenfrith. In the latter case, there was a church dating to 1207 and a community shop opposite the castle. I understand the shop was run by the women of the village, for it served yet more wonderful home-made cakes and tea (tea and cakes cost only £1.50 for two persons). It also sold tasteful touristy souvenirs, garden plants and locally made craftware like knitted objects or lace. To sum up, this pleasant region of Britain is so relaxing and so full of interest that we shall surely return.