On June 30, the Jiaozhou Bay Bridge was officially opened, becoming the world’s longest bridge to run over water. It connects the Huangdao District of Qingdao with the city proper and is 139,400 feet in length. That’s 26.4 miles (46.5km).
(I just googled “Jiaozhou Bay Bridge marathon” and yes, someone has already had the idea: New Bridge Marathon Opportunity in China)