The H.C. Andersen Marathon (HCA Marathon) is a marathon in Odense, Denmark, which was established in 2000. From 2006 onwards, the event has included a half marathon and from 2017 a 10K race "Run the last 10". HCA Marathon is named after the Danish Faity-tale writer Hans Christian Andersen. HCA Marathon is the worlds fastest marathon in 2019. On average the runners finish the marathon in just 3:51:22 which is just 8 minutes 50 second a mile. HCA Marathon is also the marathon with the cleanest air in the world. [1]