The Plus 15 or +15 Skyway network in Calgary, Alberta, Canada, is the world's most extensive pedestrian skywalk system with a total length of 16 km (10 miles) and 59 bridgeshttp://www.downtowncalgary.com/business/dynamic.php?pageId=22 Downtown Calgary - Facts and statistics. The system is so named because the skywalks are approximately 15 feet (4.6 metres) above street level.