National Trust–run Dinefwr is a large, landscaped estate just to the west of Llandeilo, home to fallow deer and a herd of rare White Park cattle. Recent archaeological digs uncovered remains of a roman fort here. At the estate's heart is a wonderful 17th-century manor, Newton House , made over with a Victorian facade in the 19th century. It's presented as it was in Edwardian times, focusing particularly on the experience of servants in their downstairs domain; recordings start as you enter each room. Other rooms recall Newton's WWII incarnation as a hospital. The tearoom serves Welsh set teas, sarnies, Welsh cakes and Bara Brith.
The castle is set on a hilltop in the southern corner of the estate and has fantastic views across the Tywi to the foothills of the Black Mountain. In the 17th century it suffered the indignity of being converted into a picturesque garden feature. There are several marked walking routes around the grounds, some of which are accessible to disabled visitors.
Bus 280 between Carmarthen and Llandeilo stops here.