Sidney is the most populous city in Australia with over 4 million people. It is located on the southeast coast and is known for landmarks like the Opera House, Harbour Bridge, and its many beaches. The Opera House was built in 1973 and features performance spaces while the Harbour Bridge, constructed in 1932, was the first bridge built across the harbor. Sydney has a humid climate with mild winters around 12 degrees Celsius and hot, sometimes over 40 degrees, summers averaging 23 degrees.