Now that I've started rooting around for Abraxas material, I'm amazed how much concept work we did. I've hardly even scratched the tip of the iceberg so far, what with the clothing and architecture for each city-state, the flora and fauna inspired by Dougal Dixon's book After Man, the adventure locations, history, NPCs, and on, and on.
Neill Blomkamp's written-off concept work for the aborted Halo movie apparently cost several million dollars, and although we didn't get anywhere near that figure, the principle of concepting in games is the same as in movies. It makes more sense to get these details worked out before you set 100 coders, modellers and animators working away on the thing.
The idea behind the Vadem Causeway was so that players in the MMOG could rapidly move between the main "safe" locations (the five cities) but, if they wanted to travel to smaller towns or go exploring off the beaten track, they would need to strike out on foot or get hold of a sky car.
The Vadem Causeway is not a physical road but a network of teleportation routes extending between archways close to each city. The Vadem gates consist of raised platforms with steps leading to a circular arch of ancient star-metal. Each gate transports the user to the next on the circuit, allowing rapid travel from city to city. A rapid burst of light is seen streaming away from the arch after a person steps through.
As the Vadem Causeway is a potential problem in wartime, each city has its own safeguards against an influx of enemy soldiers appearing outside its walls. Utesh is protected by the straits that cut it off from the mainland. Vertis has constructed a grille that can be dropped across the archways. Argistillum has a dam that, if opened, floods the vicinity of one archway; the other is kept dead in the sights of the city's one plasma cannon. Tamo Anchan has surrounded its archways with high walls with only a narrow gate out; Eibon relies on its own city walls and the fact that any invading army would have to endure the scouring desert winds.