On the east bank is Ynysangharad Park, where there is an Arts and Crafts lido, designed in the 1920s and opened in 1923. It is now disused, but is grade II listed, as it is one of the earliest outdoor lidos in South Wales. On the west bank, the river is joined by the Afon Rhondda, before it sweeps to the east in a large bend. The A4058 dual carriageway crosses the bend at an angle, and as the river resumes its southward course, it is crossed by Machine Bridge, which is also known as Pont y Doctor, as it was built by Dr Richard Griffiths in 1809, as part of a tramway to carry coal from the Hafod Uchaf pit to the Glamorganshire Canal. It has three arches, and was widened around 1910, in an early use of reinforced concrete. Some of the 19th century fabric remains, and is thought to be the earliest multi-span railway bridge still in existence in the world. Two more modern road bridges are located on its south side, and further downstream is Castle Bridge, a narrow structure with three arches dating from the early 19th century. It formerly carried a road, but is now only used by pedestrians. Next there is a large, crescent-shaped weir, which was built in 1834-5 to provide water power to the Treforest Tinplate Works. The sluice to control the flow of water to the works is at the western end of the weir, and probably dates from a little later. The works continued in operation until 1939, and a fish ladder was added in 2003, to allow migrating fish to access the upper river. Many of the building still exist, some distance to the south of the weir, including a casting house, a workshop, a tinning house, a smithy, a rolling mill, and the retaining wall for the leat. The leat had seven sluices with gates to feed the works, but all have been bricked up.