|Location Map ( geo)|
|Distance:||6.6 miles (10.6 km)|
|Meets:||A97, C73H (Moray), C73H (Moray), C73L (Moray)|
|Route outline (key)|
The C100S follows the River Deveron downstream from Huntly, with the road criss-crossing the county boundary. It starts on the A97 at Costlyburn, and heads north for a while before turning towards the river. It almost reaches the riverbank at Avochie, and then turns north east, passing into Banffshire just before Rothiemay. After a couple of miles of being the C73H (Moray), the road re-crosses the boundary and follows the river around a great meander for about a mile and a half, before returning to Banffshire. This section of the route is isolated from the rest of Aberdeenshire's road network.