The Lake Pontchartrain Causeway in New Orleans is the longest bridge in the world over a body of water, with a total length of 38,6 km (24 miles). It was completed in 1956. The Bang Na Expressway in Bankok, Thailand is even longer, at 54 km (33.5 miles), but mostly is an elevated highway. However, they are soon to be outdone by the 79.6 km Xian-Zhengzhou high speed railway bridge being built in China. It will be known as the Wei River Bridge. The most expensive bridge is the Seto-Ohashi-Kojima bridge in Japan. At 13,22 km (8,21 miles) long, it was built in 1988 at a cost of $8.3 billion. The world’s largest natural bridge is the Rainbow Bridge, tucked away among the rugged, isolated canyons at the base of Navajo Mountain, Utah, USA. It is a natural wonder. From its base to the top of the arch, it reaches 88,4 m (290 ft) – nearly the height of the Statue of Liberty – and spans 83,8 m (275 ft) across the river. The top of the arch is 12,8 m (42 ft) thick and 10 m (33 ft) wide.