1) Town in Powys 
==History== Up until the mid 18th century most of the Swansea Valley was thickly wooded and sparsely populated. The placename Ystradgynlais, meaning `vale of the river Cynlais` - Cynlais may be a personal name, or derive from cyn (`chisel`) and glais (`stream`) - is first recorded in 1372. In the 1600s there were only a couple of houses by t...