The B180 is a cross-country road in south County Down. It was originally unclassified but gained its number in the late 1920s.
The road starts on the B27 in the valley of the River Bann to the east of Hilltown and heads east. We climb out of the valley but initially remain low down in comparison with the Mountains of Mourne clearly visible to the right. After crossing a stream we skirt the northern side of the mountain range before running along the edge of the valley of the River Shimna. This takes us to Tollymore Forest Park, whose northern edge we follow into Bryansford.
On the far side of the village a spur of the B180 turns off to the right. It heads southeast, still along the valley of the Shimna, and presently enters Newcastle along Bryansford Road. A mini-roundabout is then reached, where traffic for the town centre and the north is signed to turn left, whilst traffic for the south is signed to turn right; the B180 goes this way. We cross the river and shortly reach the A2 one-way loop (formerly B125) on the southern side of town. The spur ends here and traffic is forced to turn left.
If we return to Bryansford and continue ahead along the mainline of the B180 we go through a ridge and then reach the A50. There's a long staggered crossroads to the right, then our road continues along its easterly course. It crosses the River Ballybannan and then zigzags through the village of Maghera. After a couple of miles of undulating fields we reach a T-junction on the original line of the A2. That road has now been rerouted so we TOTSO left onto its pre-bypass course and follow Old Road to a T-junction on the main road's present line just to the west of Dundrum.