Stanford's history podcast (see Stanford on iTunes U) has a great lecture by Patrick Hunt about his quest for finding the exact route Hannibal took across the Alps. In 218 BCE Hannibal evaded a Roman force marching from the Mediterranean coast by turning inland up the valley of the Rhône. His exact route over the Alps has been the source of scholarly dispute ever since ancient times. Since 1994, the Stanford Alpine Archeology Project has explored, excavated and conducted first-hand archaeological research in the Alps.
By now, Patrick Hunt has a pretty good idea where the exact passage might have been. Such a large army passing will certainly have left their traces and he is intent, with the help of national Geographic, to try and prove his theories. The lecture is a very exciting account how he got to his conclusions. The only barriers between now and the moment of either corroboration or refutation are bureaucratic. An archaeologist can't take a grain of sand without permits. So far he has worked with survey permits, the next step is to be able to take samples and start digging.