Complex sentence: The Plus 15 or +15 Skyway network in Calgary, Alberta, Canada, is the world's most extensive skywalk with a total length of 16 km. The system is so named because the skywalks are approximately 15 feet (5 metres) above street level.
Split into simpler sentences: The Plus 15 or +15 Skyway network in Calgary, Alberta, Canada, is the world's most extensive skywalk. It is so named because the majority of its skywalks are 15 feet (5 metres) above street level.