World's longest sea bridge
Recently opened in China, connecting Hong Kong to the mainland. 55 km long, including a 7 km underwater tunnel to allow shipping traffic to pass over it:
More cool pictures & factoids here (a). Perhaps it was built for mostly symbolic reasons?
But some in Hong Kong have questioned the purpose of the bridge, saying no one really needed it and that it's largely an attempt to symbolically bring Hong Kong closer to the mainland.
Looks like most of our longest bridges are in China (a).