Llansteffan (sometimes Llanstephan) sits between the Taf and Towy rivers on the Three Rivers Estuary in Carmarthenshire, South West Wales. The parish of Llansteffan consisted of two very distinct villages with separate churches: Llansteffan by the estuary and Llanybri on the hilltop inland.

Wales' most famous poet Dylan Thomas, who lived some 4 miles away at Laugharne, had strong family links to Llansteffan. The triangle formed by Llangynog, Llangain and Llansteffan constitutes Thomas' "breeding-box valley", as he once put it. His mother's family, the Williamses, lived in the triangle, in farms such as Waunfwlchan, Llwyngwyn, Maesgwyn and Penycoed.

Llansteffan Castle is located south of the village overlooking the strategically important estuary. The castle carries a tumultuous history. It was first held by the Normans, who built a timber structure on the site.

In 1146, the castle was captured by the prince of Deheubarth but the Normans managed to recapture the castle in 1158. However, they did not have much luck and the Welsh took the castle once again in 1189. Not soon after the castle fell into the hands of the monarchy, and was given to the Norman family of the de Camvilles. They saw two attacks by the Welsh, the first in 1215 and the second in 1259. On both occasions the castle was burnt and captured by the attackers but the Normans managed to regain it.

It was during 1215 that the de Camvilles built the castle's Inner Gate, which is still well-preserved. Later in 1338, the original timber structure was refortified in stone and that same year, the de Camville dynasty died out and Llanstephan castle was passed to Robert Penrees. However, in 1377 the Crown took the castle once again but allowed the Penrees family to continue living in the castle.

Of course, the castle could not go for years without facing Owain Glyndwr at least once. So he came to threaten the English sovereignty during the 15th century, and the King ordered Sir John Penrees to strengthen the castle. This did little to stop Glyndwr and he managed to capture the castle. Before long it returned to the hands of the king, and in 1495 was given to Sir Henry VIII's uncle Jasper Tewdwr. It sadly fell into a state of disrepair, but the romantic ruins of the castle are now in the hands of Cadw, who make sure that this magnificent monument can still be visited.

Notable features of Llanstephan castle include a curtain wall, a well, and a Great Hall. However, the best feature is the Great Gatehouse, built in the 13th century, with two D-shaped towers that date back to 1280. Major modifications were made to the castle by Tewdwr in the 15th century, when it was changed from a reception area into grand living quarters.