The Nicaragua Canal
I doubt it'll happen - just about every mega-project that flares up in the news never actually happens - but one thing in this article grabbed my attention.
" Many have been asking whether Central America needs two canals, even in an age of growing world trade. "
No-one who cared about free trade would ask that. Competition is Good. While there are other routes between the Atlantic and the Pacific, they are either very long (around south America) or not reliably open (Northwest Passage). The Panama canal is also not big enough for many modern ships, and still won't be even after the current upgrades are complete (see image to right). Broadly speaking, the larger your ship the cheaper it is to run per ton-mile of cargo, and it's less polluting too. And, of course, shorter routes between the same two ports are also cheaper.