The exact route that Hannibal took through the Alps is not known and may never be known. Instead, historians and academics have squabbled for centuries over the facts we do know and attempted to prove one route or the other. The exact route is enormously important for exactly no reason at all – it tells us practically nothing that leads to any important understanding in the present day. Having read a whopping six books on the subject and considering myself fully qualified to have an opinion on the subject, I will now weigh in with my thoughts.

Let's start out with what we know about the pass. Between Livy and Polybius, we find the following hints and qualifications:

• Room at summit to camp 25,000 or more soldiers, with their pack animals, weapons and elephants.
• It must be high enough that last year's snows were still on the ground in places.
• The first part of the descent must be narrow and steep.
• The summit should offer a view of the plain of the Po River and Turin.
• Turin should be a three-day march from the summit.
• The summit should be one day's march from a gorge called the "white rock place".
• The beginning of the journey into the Alps, where Hannibal left the Rhone river, should be on the edge of territory of the Allobroges tribe.

The Col de Clapier pass is the favorite of Serge Lancel and Patrick Hunt. John Prevas holds out for the Col de Traversette, because one of the features mentioned by Polybius is a "white rock place, which Prevas was unable to find within a day's march of the summit (but Dr Hunt claims to have found such a place). The folks over at livius.org favor the Col de Montgenèvre pass, but I think they favor the evidence of Livy and ignore some key points from Polybius. Others favor Mont Cenis, Col du Petit Saint Bernard, Col du Montgenèvre and Col de la Croix.

As the picture below depicts, the crossing itself was brutal. Imagine you're a soldier walking along a narrow path (less than 20 feet wide in many places) behind 25,000 other soldiers walking in the snow ahead of you. Now, add a couple thousand pack animals and top it off with a bunch of elephants. That's not a path you want to be walking. Now, add in a bunch of hillmen up above you hurling down rocks to try and knock you off the path and into the gorge below. Hannibal was lucky he only lost half of his men in the crossing - oh, and by the way, the descent was worse, due to narrow passages covered in slippery ice that had men and animals slipping over the side with great regularity.

I feel fully qualified to end this debate forever: it was Col de Clapier. I am as certain of this as I am of the general mathematic underpinnings of the Dark Energy theory. The Traversette is very narrow and by all accounts just a ledge, there would have been no way to camp an army at the summit (and the sources are pretty firm on this point) and it's more than a three day march from Turin. Several of the passes, such as Col du Montgenèvre, just aren't high enough for snow to survive year to year and most of them do not have a view of the Po valley from their summits. Col de Clapier has a nice view of Turin from the summit (follow the link and see for yourself), as only one or two others do.

For the most part the defenders of each pass ignore facts that don't support their pass and play up the ones that do. For example, we know that there was a view of the Po Valley from the summit by this passage in Polybius:

As it was now close to the setting of the Pleiads [mid-October] snow had already gathered on the summit, and noticing that the men were in bad spirits owing to all they had suffered up to now and expected to suffer he summoned them to a meeting and attempted to cheer them up, relying chiefly for this purpose on the actual view of Italy, which lies so close under these mountains, that when both are viewed together the Alps stand to the whole of Italy in the relation of a citadel to a city. Showing them, therefore, the plain of the Po, and reminding them of the friendly feelings of the Guals inhabiting it, while at the same time pointing out the situation of Rome itself, he to some extent restored their spirits.
Polybius, Book III, 54.

Since this passage won't work for Col de Montgenèvre, the folks over at livius.org say, "[the view of the Po Valley] is the least important, because Hannibal's speech was probably invented. This was a very common practice in ancient historiography: the reader expected short speeches in which the actors explained what they were doing and why." I might go for this explanation (Polybius often has generals addressing the troops before an important battle) if it were the only way to explain the passage, but since there is another pass that does have such a view, I'm not buying it. Also, it's true that in real life generals often address the troops before battle.

Here is Col de Clapier in Google Map form:

View Larger Map

If you zoom out a bit, you can see the Italian town of Susa, where Hannibal's descent will end, a few miles to the southeast. If you look west fifty miles or so, you will see Grenoble, which is on the Isere river. Following the Isere to where it meets the Rhone river, we find ourselves on what it thought to have been the southern edge of the Allobroges territory. The Allobroges furnished Hannibal his guides through the first part of the journey into the Alps and Polybius makes it clear that Hannibal skirted their territory. You can also see on the map that the pass has plenty of room for a whole army. If you follow the link to Col de Clapier, you will see a picture of the descent from the summit and it is indeed steep. All of the facts just fit and I can think of only one reason this wasn't settled centuries ago.

I should also mention here, however, that the terrain has changed in 2,200 years. It's possible that landslides and glaciers have changed the landscape so much that the actual pass Hannibal used is disfigured to the point where it isn't recognizable. Personally, I don't think 2,200 years is enough time for that much change, but it's not out of the question.

If you want to fly along Hannibal's route, one of Dr Hunt's students has produced a video using Google Earth that traces the route. It's pretty darn harrowing, as you can see. Disregard the cities, roads and bridges you see, those obviously weren't there 2,200 years ago. That bit in the middle, where they leave the valley and pop up over the Col Du Clapier, seems awfully steep, but Dr Hunt claims to have walked it himself a number of times.

I suspect the question isn't settled because it has made a wonderful field of study for academics over the generations. Many of them, such as Prevas, Hunt and Lancel, have managed to spend their summers in scholarly hiking of the Alps looking for evidence to support their theories and no one wants to put and end to that. There are papers to write and maps to pore over and archeological items to be unearthed. I have no doubt that there are also conferences to attend (held, out of necessity, in lovely five-star hotels all over the world), books to profit from and students to hang on your every word. So, no, even if a monument is dug up saying, "Hannibal was here", this debate will continue for as long as we have folks to debate it.

Note: this entry is part of a series called "Hannibal", which contains the following entries:
     Hannibal Studies
     The Punic Wars
     Hannibal and Rome
     Hannibal in the Alps
     Greatest General of All Time?