"In 1818, the US began building a fort near the New York-Quebec border to defend against invasions from Canada. After two years of construction, they realized the fort was actually on the Canadian side. They abandoned it and named it Fort Blunder." The overgrown foundations of a military installation sit amidst dense forest on the banks of Lake Champlain. It wasn't a complete loss; the locals got a great laugh and scavenged the unused stone for their own buildings.