after it opened in 1973 it became a major tourist attraction and symbol of the city. The progressive reduction in tariff protection from 1974 began the transformation of Sydney from a manufacturing centre focused on the domestic market to a "world city" providing financial, commercial, cultural and educational services to local residents and Australian and overseas markets. From the 1980s, overseas immigration to Sydney grew rapidly, with Asia, the Middle East and Africa becoming major sources of immigrants. By 2021, the population of Sydney was over 5.2 million, with 40% of the population born overseas. China and India overtook England as the largest source countries for overseas-born residents. Geography Topography Sydney is a coastal basin with the Tasman Sea to the east, the Blue Mountains to the west, the Hawkesbury River to the north, and the Woronora Plateau to the south. Sydney spans two geographic regions. The Cumberland Plain lies to the south and west of the Harbour and is relatively flat. The Hornsby Plateau is located to the north and is dissected by steep valleys. The flat areas of the south were the first to be developed as the city grew. It was not until the construction of the Sydney Harbour Bridge that the northern reaches of the coast became more heavily populated. Seventy surf beaches can be found along its coastline with Bondi Beach being one of the most famous. The Nepean River wraps around the western edge of the city and becomes the Hawkesbury River before reaching Broken Bay. Most of Sydney's water storages can be found on tributaries of the Nepean River. The Parramatta River is mostly industrial and drains a large area of Sydney's western suburbs into Port Jackson. The southern parts of the city are drained by the Georges River and the Cooks River into Botany Bay. There is no single definition of the boundaries of Sydney. The Australian Statistical Geography Standard definition of Greater Sydney covers and includes the local government areas of Central Coast in the north, Hawkesbury in the north-west, Blue Mountains in the west, Sutherland Shire in the south, and Wollondilly in the south-west. The local government area of the City of Sydney covers about 26 square kilometres from Garden island in the east to Bicentennial Park in the west, and south to the suburbs of Alexandria and Rosebery. Geology Sydney is made up of mostly Triassic rock with some