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
Geography of the Isle of Man the Ordovician period. There is a belt of younger Silurian rocks along the west coast between Niarbyl and Peel, and a small area of Devonian sandstones around Peel. A band of Carboniferous period rocks underlies part of the northern plain, but is nowhere seen at the surface; however similar age rocks do outcrop in the south between Castletown, Silverdale and Port St Mary. Permo-Triassic age rocks are known to lie beneath the Point of Ayre but, as with the rest of the northern plain, these rocks are concealed by substantial thicknesses of superficial deposits. The island has significant deposits of