sentences:  The route starts in Castlebay at about 60 ft falling quickly to sea level before rising to 100 ft around the 1-mile mark.The next 0.5 miles is mainly downhill and then the course undulates between sea level and 50 ft until the 4-mile mark.From mile 4, the course climbs gradually as the route starts to head east, peaking at around 170 ft just past the 5.5-mile stage.