The CN Tower is a communications and observation tower in Downtown Toronto. Standing 553.33 metres (1,815.4 ft) tall, it was completed in 1976, becoming the world's tallest free-standing tower at the time. It remains a symbol of Canada, attracting more than two million international visitors annually. Its name "CN" originally referred to Canadian National. The railway company built the tower. Later the name CN Tower became common in daily usage. In 1995, the CN Tower was declared(宣称) one of the modern Seven Wonders of the World by the American Society of Civil Engineers. It also belongs to the World Federation of Great Towers, where it holds second-place ranking(排名).