MANY are the tools designed to help travellers decide on the best way to reach B from A. Search engines allow you to order results by ticket price, number of connections, journey duration and carbon-dioxide emissions. What you can't usually do, though, is stipulate that you would prefer to travel by ox cart or rapid military march. That's because the modern travel-booking tool is a lot less fun than a new creation from a team of historians and IT specialists at Stanford University.

ORBIS is an interactive map of the Roman Empire as it was around 200AD. The "geospatial network model" includes 751 sites, 84,631 km (52,587 miles) of road or track, and 28,272 km of navigable rivers and canals—not to mention 900 sea routes. Among its various capabilities, it allows users to work out how long it would have taken and how much it would have cost to travel from any given point in the empire to any other, given a particular mode of transport, time of year and proposed route. It's a bit like a Roman routeRANK.

For example, a London-based merchant heading bravely to Rome on horseback in April would have spent almost 22 days travelling. The suggested quickest route actually seems rather lengthy, involving sailing down the Channel and the Bay of Biscay, then cutting eastwards by river and road across the south of France to the Mediterranean, and thence by sea to Rome. But riding all the way through Europe would actually take 13 days longer. Only with a horse relay (and rather a lot more denarii) does the land route become faster; such a trip takes less than nine days.

This example only scrapes the surface of what ORBIS offers. It's well worth having a play.