The Gwaun Valley (Cwm Gwaun) begins in Fishguard, where the namesake river runs into the sea. It is a perfect little tucked away landscape wonder.

The Rough Guide describes as one of the great surprises of Pembrokeshire. Yet, despite its seclusion, the Gwaun is easily reached by road and footpath.

The steep-sided valley was formed out of an epic geological convulsion, carved in a V-shaped by the rushing waters from melting glaciers. Geologists list it as one of the most important meltwater channels in Britain from the last Ice Age.

It runs from Lower Town Fishguard towards the Preseli Mountains, where the Gwaun river rises to the east of Pontfaen. For most of its 10 miles, it is within the confines of the Pembrokeshire Coast National Park.

The valley is a pure rural idyll, thick with beech and hazel, ash and oak. On recent forays, ornithologists report sightings of pied flycatcher, wood warbler, redstarts, marsh tit, nuthatch and treecreeper.

The area abounds in history, legend and tradition. In the Gwaun valley, the villagers of Pontfaen and Llanychaer follow a distinct observance that sets them apart.

Once a year they mark the old Julian calendar, which operated before 1752, celebrating New Year’s Day or Hen Galan, on the 13th of January. Many children miss school and tour the villages, singing old songs. Householders give them traditional tribute, or Calennig, for their trouble.

Another very real link to the past is the old pub at Pontfaen, the Dyffryn Arms. In the same family since 1840, it is a still working reminder of the country pubs of earlier generations.

This is “Bessie’s Pub”. The namesake landlady, Bessie Davies, herself may pour you a pint from a jug and hand it through a hole in the wall, with helpful hints about what to see in the area.

There’s a relic from the deep past in the circular churchyard at St Brynach’s in Pontfaen. Two pillar stones with inscribed Latin crosses are thought to date from between the 6th and 9th century, so may even be contemporary with the saint himself. Brynach is said to have had angelic visions at the nearby Carn Ingli (Mountain of the Angels), near Newport.

And, still in the valley, at Llanychaer, there is the site of an Iron Age defensive enclosure behind the village pub, the Bridgend Inn.

One of the most impressive ancient sites in this area is the four ancient stones in Parc Y Meirw (Field of the Dead), just above the Gwaun, half way between Llanychaer and Garn Fawr. It is possible that the bluestones, quarried in the Preseli hills above, were taken past this point and down the hill to the sea to be sailed away to the Stonehenge building site.

The Preseli hills themselves abound with myth and mystery. There is a celebrated literary guide to this magical past. The Mabinogion is a collection of 1000-year-old Welsh tales, a number of them set in this landscape.

One of the most colourful derives from the impressive Stones of the Sons of Arthur, on the flank of the mountains’ highest point, Foel Cwmcerwyn.

According to the Mabinogion, in the story of Culhwch and Olwen, the enchanted giant boar Twrch Trwyth kills four of King Arthur’s champions in a big battle at this spot. It’s one of a number of places in the Preselis linked to the mysterious, magnificent Dark Ages king.

There is more recent and very real, history. In 1943 the RAF bombed the tunnel at Castell Forlan on a disused railway line into the Preseli foothills, in a successful test for the famous “Dam Busters” bouncing bomb of Barnes Wallis.

And the poet Waldo Williams is commemorated with a memorial stone next to the Gors Fawr stone circle. Williams, one of the finest 20th-century Welsh language poets, lived in Mynachlog-Ddu beneath the hills and extolled them in one of his best-known poems, Preseli.

The Gwaun Valley and surrounding areas are easy to explore if spending 48 hours in Fishguard or Newport. Take a step back in time.