What is gravel biking? It is an activity growing in popularity and a fun way to explore the amazing scenery of the Haliburton Highlands while getting in a good workout at the same time. “Gravel” is any terrain between the steep, rocky inclines of mountain biking, and the smooth asphalt of road biking. Routes could be sideroads, decommissioned service roads, forest access and logging roads, or just really chunky, hard to access roads or paths that can take you somewhere really remote and special.