Castell Gwallter is located on a hill above the old village of Llandre (Welsh: Llanfihangel Genau'r Glyn) in northern Ceredigion, Wales, four miles northeast of Aberystwyth. It is an early twelfth century motte and bailey castle which seems to have been left to decay after the mid twelfth century. The mound and bailey can be seen and is protected by a ditch, although there does not appear to be any stone work remaining. The site is off the B4353 on private land (but can be viewed) about a mile west of Llandre, north of Aberystwyth.