|Length:||1.8 miles (2.9 km)|
|Met (1961):||A470, A4160, A4055, A48, A4119|
|Now part of:||A4119|
|Route outline (key)|
The B4259 is described in the 1922 Road Lists as Loop in Cardiff.
It started in Butetown, on the edge of what is now known as Cardiff Bay, just to the north of the southern end of the A470. It headed west, quickly crossing the River Taff before bending round to the right. It continued north via Grangetown and went under the Cardiff to Swansea railway line before ending on the A48 just across the river from the castle.
The road survived at least until the 1960s but is now part of the A4119.