While Toronto’s CN Tower no longer holds the world record for tallest building in the world, it still holds the record for the world’s tallest metal staircase.

The idea for the CN Tower originated from the 1968 Canadian National Railway’s desire to build a large television and radio communication platform that would serve the Toronto area and demonstrate the strength of Canada and its industry. It surpassed the height of the Ostankino Tower while still under construction in 1975, becoming the tallest free-standing structure on land in the world for the next 31 years. The concrete structure stands at 553 meters (1,815 feet) tall.

Inside, a metal staircase winds through the tower. It takes 1,776 steps to reach the main deck, and 2,579 steps to reach the SkyPod level. The stairs are not typically open to the public—they’re intended for emergency use only—but twice a year visitors who want to scale the massive structure have the opportunity to join charity stair-climbing events. On average, climbers take about half an hour to complete the climb. The record for fastest climb is held by Brendan Keenoy, who reportedly managed the feat in seven minutes and 52 seconds in 1989—though the accuracy of his time has been the subject of debate.

The CN Tower’s claim as the world’s tallest free-standing structure was surpassed on September 12, 2007 by the Burj Khalifa (formerly known as Burj Dubai). It has since also been surpassed by the Guangzhou TV & Sightseeing Tower, which was completed in 2009.

Today, the Toronto tower is the ninth tallest free-standing structure in the world, and still holds the title of tallest free-standing structure on land in the Western Hemisphere. Despite this, the CN Tower remains the signature icon of Toronto’s skyline, and a symbol of Canada.