Sources

The workings.

Every interactive on this site is a reconstruction: real terrain, real primary sources, and honest guesswork where the record runs out. Here is where it all comes from.

Hannibal's Crossing

• Polybius, The Histories, Book 3 — the closest thing to an eyewitness account. Polybius interviewed survivors and walked parts of the route himself. The army figures (46,000 in, ~26,000 out) and the fifteen-day crossing come from him.
• Livy, Ab Urbe Condita, Book 21 — written about two centuries later, more dramatic and less reliable, but the source of several famous episodes along the march.
• The three candidate passes reflect the main scholarly camps. Neither Polybius nor Livy names the pass, and historians have argued about it for over two thousand years — so the map lets you march all three instead of declaring a winner.
• Elevation data: Terrain Tiles on AWS — © Mapzen and USGS, rendered as a real heightfield of the western Alps.

Routes, day counts and figures are best-effort reconstructions, not settled fact. If you spot an error, send word — corrections are gratefully received.