Dyffryn Ardudwy is the remains of a twin-chambered barrow. The dolmens were built in separate periods, with the earlier monument being incorporated into the later phase of construction. Both dolmens would have formed chambers of one massive cairn.

The western dolmen is the older of the two, dating from the early Neolithic period. When first built, it would have been encompassed by a circular cairn. It forms a rectangular chamber, crowned by a sloping capstone, and fronted by two high pillars.

The eastern dolmen is the later of the two. When built, it was covered with a large, wedge-shaped cairn that extended to incorporate both monuments, with the later dolmen fronting onto the tomb's forecourt.

Although the proximity of local buildings has an undeniable impact, this is still a remarkably pleasant site (helped largely by the rural landscape to the east and views out over Cardigan Bay to the west and south). The twin-chambered arrangement is highly unusual and well-deserving of a visit.