The bridge which now carries Castle Street over the Taff was built downstream of the site of the previous one in 1859, a decade after IK Brunel diverted the river (to its present course) to provide a suitable site for what is now Cardiff Central Railway Station. This created a long enough site for the station on the east-west axis, and protected the site from flooding. In 1851, Cardiff’s town clerk was instructed to “write to Mr Brunel pointing out the nuisance and injurious effects to the Public Health, arising from the old bed of the river Taff”. Land where the river once flowed was set aside for sport, and now hosts the Millennium Stadium and Cardiff Arms Park.
The fact that streets like Quay Street and Womanby Street whose locations are now several hundred metres from the river proves that the river was redirected from its original course with a huge, sweeping meander straightened out. It also proves that the river was navigated by Vikings (Womanby has Viking origins).
Part of the eastern abutment of the 1795 bridge can still be seen near the landing stage in Bute Park (literally at your feet in the vicinity of the cache). Go to the other side of the river for a better view! A famous Turner painting will give you a fabulous insight into the past prior to the development of photography.