The Isle of Portland is a limestone island situated five miles to the south of the resort of Weymouth, making it the southernmost point of Dorset. Portland is not actually an island because the island-like land mass is connected to the mainland by Chesil Beach which is four and a half miles long by just one and a half miles wide. The breakwater which forms one of the largest harbours in the world, some 2130 acres, was started in 1849. Apart from the sea, the major Portland industry was quarrying for the famous Portland Stone. This has been used on many famous buildings all over the world including St Paul's Cathedral in London and the United Nation Headquarters in New York.