1. Slender masonry arches, designed by Isambard Kingdom Brunel, carrying his 1840s Taff Vale Railway over Mill Street. The span over the Rhondda is some 110'. Part of the first all-locomotive haulage modern railways in Wales.
(Site entry by S.R.Hughes for Buildings of Glamorgan, John Newman, 1995)
B.A.Malaws, RCAHMW, 22 April 2003.

2. The first Taff Vale Railway Rhondda crossing of 1841 was single-track standard-gauge on Brunel's 110ft skew single-span stone arch. Doubling took place from 1857 but with two-spans and a river pier. The sharp leftwards curve into the Rhondda valley from the Taff valley route caused a number of derailments. This caused a second seven-arch double-track crossing to be built in 1861-2. At the north end a cutting of 1872 allowed direct traffic between the two valleys. This route is now filled in.
(A Guide to the Industrial Archaeology of South East Wales, AIA, 2003)
Construction work on the Taff Vale Railway began in 1837 with the ceremonial laying of the first stone to the viaduct across the River Rhondda at Pontypridd by Lady Charlotte Guest, wife of Sir Josiah John Guest of the Dowlais Ironworks. The viaduct has a skewed river span of 33.5m, which was an impressive engineering achievement for its date. The railway was widened to a double track 1845-61, which required the addition c1861 of a separately constructed viaduct abutting the earlier viaduct.
(Source Cadw listing description, 2/26/2001)
B.A.Malaws, RCAHMW, 10 November 2005.