I thought today I would signpost a website that I suspect many people will find rather "narrow", and perhaps even think of as "nerdish". But if you have an interest in the Roman world of the New Testament, you will find it fascinating.

It is ORBIS, the Stanford Geospatial Network Model of the Roman World.

This wonderful free resource is far more than an atlas or a static collection of maps.

As the Home page states

Conventional maps that represent this world as it appears from space signally fail to capture the severe environmental constraints that governed the flows of people, goods and information. Cost, rather than distance, is the principal determinant of connectivity.

For the first time, ORBIS allows us to express Roman communication costs in terms of both time and expense. By simulating movement along the principal routes of the Roman road network, the main navigable rivers, and hundreds of sea routes in the Mediterranean, Black Sea and coastal Atlantic, this interactive model reconstructs the duration and financial cost of travel in antiquity.

Taking account of seasonal variation and accommodating a wide range of modes and means of transport, ORBIS reveals the true shape of the Roman world and provides a unique resource for our understanding of premodern history.

Think of it as Sat Nav for the New Testament.

The underlying model in ORBIS is complex and sophisticated, even though it is based on a simplified version of the giant network of cities, roads, rivers and sea lanes that framed movement across the Roman Empire. It broadly reflects conditions around 200 CE but also covers a few sites and roads created in late antiquity.

The model consists of 632 sites, most of them urban settlements but also including important promontories and mountain passes, and covers close to 4 million square miles of terrestrial and maritime space. 301 sites serve as sea ports. The baseline road network encompasses 52,587 miles of road or desert tracks, complemented by 17,567 miles of navigable rivers and canals.

Sea travel moves across a cost surface that simulates monthly wind conditions and takes account of strong currents and wave height. The model's maritime network consists of 1026 sea routes (linking 513 pairs of sites in both directions), many of them documented in historical sources and supplemented by coastal short-range connections between all ports and a few mid-range routes that fill gaps in ancient coverage. Their total length, which varies monthly, averages 119,806 miles. Sea travel is possible at two sailing speeds that reflect the likely range of navigational capabilities in the Roman period. Maritime travel is constrained by rough weather conditions (using wave height as proxy). 158 of the sea lanes are classified as open sea connections and can be disabled to restrict movement to coastal and other short-haul routes, a process that simulates the practice of cabotage as well as sailing in unfavourable weather. For each route the model generates two discrete outcomes for time and four for expense in any given month.

The model allows for fourteen different modes of road travel (ox cart, porter, fully loaded mule, foot traveller, army on the march, pack animal with moderate loads, mule cart, camel caravan, rapid military march without baggage, horse with rider on routine travel, routine and accelerated private travel, fast carriage, and horse relay) that generate nine discrete outcomes in terms of speed and three in terms of expense for each road segment. Road travel is subject to restrictions of movement across mountainous terrain in the winter and travel speed is adjusted for substantial grade.

What does all this mean? Increased understanding of the background to Paul's missionary journeys. New insight on the sea voyage of Paul that ended in shipwreck!

What can you do with ORBIS?

1. Find routes between two places

To establish a historical route from one of the sites in the ORBIS model to another, you simply select the start and destination sites from the two drop-down lists. Sites are named in accordance with The Barrington Atlas of the Greek and Roman World Routes differ depending on whether you are looking for the fastest, cheapest or shortest connection, on the modes and means (here called options) of transport, and on the month of the year.

Here's the route in Spring from Jerusalem to Rome.

2. Network Diagrams and Clustering

You can calculate the distance, time or expense to or from one site to all the other sites in the network. The ORBIS site has a tutorial video for this feature.

After calculating a network, you can display the results territorially. You can discover whether all roads really do lead to Rome.

Here's a network diagram for Jerusalem in the Summer.

3. Flow Diagrams

These aggregate the paths calculated to or from a site by segment. The popularity of individual segments are indicated by the thickness of the segment in the diagram. So they show the busiest or most important parts of the transport network.

Again, a tutorial video is provided.

Why not travel back in time and travel in Roman times?