+15

In my most recent trip to Canada I had the opportunity to explore Calgaries sky bridge system, the +15.  Named the +15 because it sky bridges are all about 15 feet above the ground.  This is intriguing since Canada is on the metric system.  More fun facts about the system

Made up of 59 bridges

First opened in 1970

16 km long, making it the longest suck system in the world.

Like the tunnel system in downtown Houston, one finds a variety of resturants, shops and services along it route.  While these are all included in the buildings that the systems connect, it still makes it easy on a cold (extremely cold) day to walk to a food court, of stretch your legs.  Of course when the weather is nice, there is an increase in sidewalk traffic and a decrease in the +15 traffic.