CHINA has unveiled the worlds longest sea bridge, which stretches a massive 26.4 miles - five miles further than the distance between Dover and Calais and longer than a marathon, Daily Mail reported on Friday. The Qingdao Haiwan Bridge, completed earlier this week, links the main urban area of Qingdao city, East Chinas Shandong province, with Huangdao district, straddling the Jiaozhou Bay sea areas. The road bridge, which took four years and cost a cool 5.5billion to build, will be open for use in the New Year and is almost three miles longer than the previous record-holder, the Lake Pontchartrain Causeway in Louisiana. That structure features two bridges running side by side and is 23.87 miles (38.42km) long. The three-way Qingdao Haiwan Bridge is a staggering 174 times longer than Londons Tower Bridge, over the Thames River - and shaves 19 miles off the drive from Qingdao to Huangdao. Two separate groups of workers have been building the different ends of the structure since 2006.