Zwifters start at sea level, breathing that salty oxygenated air before going into the sea via the Ocean Tunnel. After exiting, the climb begins. During the next 5.8 miles (9.4 km) over a 3.9% grade, Zwifters have plenty of time to get intimate with their relationship to lactic acid. And the final push, AKA the Radio Tower Climb, is brutal. Just .7 miles (1.1 km) at soul-crushing 13.7% grade. Even the genetically gifted fit folk take almost four minutes to make this ascent. And the very lucky have a Featherweight PowerUp. After a quick descent, there’s a short, false flat followed by a 350m flat and fast (flast?) sprint.