The Port of Singapore refers to the collective facilities and terminals that conduct maritime trade, and which handle Singapore's harbours and shipping. It has been ranked as the top maritime capital of the world, since 2015. Currently the world's second-busiest port in terms of total shipping tonnage, it also transships a fifth of the world's shipping containers, half of the world's annual supply of crude oil, and is the world's busiest transshipment port. It had also been the busiest port in terms of total cargo tonnage handled until 2010, when it was surpassed by the Port of Shanghai. Because of its strategic location, Singapore has been a significant entrepôt and trading post for at least two centuries. During the contemporary era, its ports have not become just a mere economic boon for the country, but an economic necessity because Singapore is lacking in land and natural resources. The Port is critical for importing natural resources, and then later re-exporting products after they have been domestically refined and shaped in some manner, for example wafer fabrication or oil refining to generate value added revenue. The Port of Singapore is also the world's largest bunkering port. The majority of ships that pass between the Indian Ocean and the Pacific Ocean go through the Singapore Strait. The Straits of Johor on the country's north are impassable for ships due to the Johor-Singapore Causeway, built in 1923, which links the town of Woodlands, Singapore to the city of Johor Bahru in Malaysia. History Before 1819 In the late 13th century, a Kingdom known as Singapura was established on the north bank of the Singapore River around what was called the Old Harbour. It was the only port in the southern part of the Strait of Malacca and serviced ships and traders in the region, competing with other ports along the coast of the Malacca Strait such as Jambi, Kota Cina, Lambri, Semudra, Palembang, South Kedah and Tamiang. The port had two functions. First, it made available products that were in demand by international markets; according to the Daoyi Zhilüe (Brief Annals of Foreign Islands, 1349) by Chinese trader Wang Dayuan (born 1311, fl. 1328–1339), these included top-quality hornbill casques, lakawood and cotton. Although these goods were also available from other Southeast Asian ports, those from Singapore were unique in terms of their quality. Secondly, Singapore acted as a gateway into the regional and international