There are many bridges on the lake, especially Pontchartrain Avenue, which is the most famous. The road consists of two parallel bridges, which were completed in 1956 and 1969 respectively. Each bridge is about 39 kilometers (24 miles) long and connects Metairie (suburb of New Orleans) and mandeville (suburb of New Orleans) on the north and south sides. This double bridge, the longest water bridge in the world, has become a relay station for the migration of a large number of purple Martin birds, which were largely unaffected by Hurricane Katrina.