One of the things I bought at Gen Con this year, was Paizo's GameMastery Map Pack: Extradimensional Spaces which I was directly inspired to do so by Dungeon Siege III's use of the Causeways.
The Causeways are an outer planar feature that allows rapid movement between one location to the next.
This is not a brand new innovation, even in video games. Games like Diablo have used them for a long time, and I know that at least in places like the Wheel of Time, where you can enter another dimension to save some time on the material plane, in terms of travelling, they have been used.
The lure of such places fits a few things though. For one, teleportation, especially as a spell, if a very powerful tool and something many players, especially those who've actually played through to the level where they can gain it, will keep in their back pocket. This may at times leave the party in the lurch as their artillery suddenly decides that after taking 40 of his 45 hit points of damage in a single stroke, to get the hell out of there.
By introducing such a manner of movement, you allow the players to bypass having teleportation. sure, they may want it, but if customizing your campaign, don't give it to them. It doesn't exist. Movement of troops and small elite forces, such as adventurers, is often done through the use of these types of causeways. This allows the players to still have a means of moving rapidly without potentially unbalancing the campaign to the point where the GM has to have some viable reason why the player's can's scry, teleport and assassinate.
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