|Length:||13.1 miles (21.1 km)|
|Meets:||A4120, B4575, B4343|
|Route outline (key)|
The B4340 is a hilly B-road in north Cardiganshire. It was originally unclassified but gained its number in the late 1920s, making it an early example of a recycled number.
The road starts in the Aberystwyth suburb of Southgate by turning off the A4120 just east of that road's junction with the A487. We run parallel to the latter for a short distance then bend sharply left to start heading southeastwards. After descending to cross a stream the road climbs gently on the far side along a more-or-less straight road. Presently the hamlet of New Cross is reached, after which the road descends steeply into the valley of the River Ystwyth.
We follow the valley upstream for a few miles. To begin with the road is somewhat above the valley bottom but after passing through Abermagwr road and river run almost alongside each other, although as we're going through a wood at this point the river is not visible. The B4575 comes in from the right and we continue upstream and leave the wood behind. Eventually there's a 180º turn to the right; we cross the river and climb out of the valley.
After crossing a saddle the road runs under the crags at Ystradmeurig, going through the village of that name and descending into the valley of the River Teifi, the same river that flows through Cardigan. Presently Pontrhydfendigaid is reached and the B4340 ends where the B4343 comes in from the left and takes on the route ahead.