From 1794 through to at least 1951, this was the East Canal Wharf of the Glamorganshire Canal.
In the foreground runs the GWR railway (the main Swansea to London line still in major use today), built by 1850 by the South Wales Railway Company, which would have had to have bridged the canal at this point.
The red brick building in the top-right is the remains of the York Hotel, which adjoins Custom House, once the administrative home of the Glamorganshire Canal when operations were moved from Navigation House in Navigation (modern-day Abercynon).
Behind where I’m stood today is Callahan Square, but in the past this would have been the wharfs that stretched all the way down to the River Taff over a mile away: Sea Lock Pond, the first of Cardiff’s great docks.
You can clearly see in this photo how the road under the GWR bridge has to drop for cars and buses to fit underneath. My guess is that the clearance was a lot less when this was still canal!
If you’re reading this in the RSS feed, my original blog post also includes a Google map showing where this photo was taken. Unfortunately I haven’t managed to get the map to appear yet in the RSS feed, so for now you’ll have to click through to my blog if you want to see the map. Sorry.