The David Dunlap Observatory is home to the largest optical telescope on Canadian soil with a primary mirror measuring more than 1.88 metres (74 inches) in diameter.
Constructed in the 1930s, the Observatory is located in the heart of Richmond Hill, Ontario. The dome building is 18.6 metres (61 feet) in diameter and the rotating dome weighs 73 metric tons. The telescope itself weighs 21 metric tons (without its primary mirror).