Llanwrtyd Wells is a small town located on the Heart of Wales Railway Line, south-west of Builth Wells. There is a sulphur spring beside the River Irfon. Nowadays, the town is famous for its annual bog snorkellin competition. Other activities include walking, fishing, birdwatching and pony trekking. In the hills northwest is Llyn Brianne, a large reservoir created for Swansea.