While reading A Path Between the Seas I learned that Panama was actually the third choice for a canal through Central America. The other proposed paths were through Nicaragua and Mexico. Neat huh?
It looks like another canal proposal might be coming to life. http://www.bbc.co.uk/news/business-12448580 It's not a true canal, but still interesting.
And if you like epic non-fiction stories of construction and colonization read A Path Between the Seas. I highly recommend it.