Billown Circuit Billown Circuit The Billown Circuit is a motorcycle road-race course used for the Southern 100, the Pre-TT Classic races and the National Road Races meetings near Castletown on the Isle of Man. Racing is held on public roads closed for racing by an Act of Tynwald, the parliament of the Isle of Man. The course is 4.25 miles (6.8 km) long and is in the parishes of Arbory and Malew. The course start-line is on the outskirts of Castletown and the course includes parts of the primary A5 New Castletown Road, A28 Castletown to Ballabeg Road, A7 Ballasalla to Port
Castletown, Isle of Man to the west Port St Mary and Port Erin. The older parts of the town are largely built of local grey limestone. At Scarlett, a short distance to the south of the town, there are the remains of an ancient volcano and various other features such as fossils and thick sheets of limestone. The A3 road connects Castletown with Ramsey via St John's, while the A5 road (also known as New Castletown Road as opposed to the Old Castletown Road which takes a more rural route nearer the coast) connects the town with Douglas to the north-east and Port Erin