The B177 is a cross-country road in north County Down. Originally unclassified, the number came to the area in the late 1920s.
Originally the road started on the A1 in the centre of Hillsborough. However, that road now bypasses the village and the B177 has taken on its former route in both directions. At the northern end our road starts at a roundabout and heads south into town along the leafy Lisburn Road, which only really becomes built-up as we approach the village centre. At the northern end of Main Street the mainline of the B177 TOTSOs left onto Ballynahinch Street, at its original western end. The other spur then continues ahead and climbs to the main square then zigzags to skirt the grounds of Hillsborough Castle. We then leave town along Dromore Road and shortly return to the A1 at a GSJ.
The mainline of the B177 heads east through town along Ballynahinch Street and skirts Hillsborough Forest Park as it climbs into open country. The B178 turns off to the left, after which the wall of the Forest Park moves away and fields become visible on both sides of the road. There's now a fairly straight road for a couple of miles which takes us to Annahilt. We run along the main street and quickly return to open country.
The road remains largely straight as it crosses the Ballynahinch River and then goes over a hill spur to cross the river again. A crossroads is then met, where the B177 originally ended on the A49. However, in the 1960s that road was rerouted and so our road now continues ahead along the A-road's former route into the town of Ballynahinch. The A49 now comes in from the left in the suburbs and takes on the road ahead into the town centre.