Tawe-Uchaf is a community in Powys, Wales. Situated north-east of Ystradgynlais in the upper valley of the River Tawe, it includes the villages of Caehopkin, Coelbren, Glyntawe, Pen-y-cae, Penwyllt and Ynyswen. It had a population in 2001 of 1,516, increasing at the 2011 Census to 1,562.There are many caves in the area, the most famous of them being Dan-yr-Ogof, one of the largest cave systems in western Europe and a popular attraction for visitors.