I don't have time to post a comprehensive reply at the moment, but I thought you might be interested in this article from Gamasutra about creating plausible obstacles.

I think it should be right up your street in this case :)

Hope it helps,

Steve

With all esle happening have the local volcano erupt and rivers of molten lava and flames cut off the city.


You could have the city sealed off (the leader was murdered, etc...) or maybe a plague is outside.

If it was a magic game then no problem ....


Flying City ??? step out and fall to your death ???



Kind of contrived for a capitol city to lose all means of communications/transport. How about having the player under oath not to leave ????

Sneftel, I can see what you mean, but both those games you mentioned (Mass Effect and Oblivion) have much larger game worlds than I would like. I would rather have a small but focused world, and not pad the edges with "barren plains". I would imagine that in a smaller world, a reasonably explorative player would be bashing up against the edges alot more than in your examples.

I like the idea of the city being cut off from supplies, and having to factor in limited supplies into the player's rise to power. I've decided that the city will be surrounded by a fast flowing river, leading to a waterfall. The bridges over the river will be retracted instead of destroyed, and that there'll be some arable lands between the city and the river. This way the city won't be at immediate risk from starvation, but it should grow as a problem throughout the game.

Quote:Original post by Kest
If it's pre-modern, you'll be somewhat limited in your choice of plausible boundaries. It's pretty easy to create them in settings that are modern or later, depending on how maneuverable your player is. For example, two tall buildings with a dumpster, pile of trash, wall, fence, or parked car between them can create a barrier.

Two examples which comes to mind.
Don't do this: STALKER. Just go 20m out of the intended area and you get (with no warning) an instant kill. STALKER made this horribly bad as this came from an invisible source in an on/off way.
Consider: Thief 1 and 2, from Looking Glass Studios (R.I.P.). The key point is that medioeval and generally old cities do have defensive walls around them which cannot be climbed easily.
As Kest noticed, there's the need for variation. Thief had quite a bit. Sometimes for example, you could instead see thuru a grate. At a certain point maybe you could find a break thuru a canal but you couldn't make it to the solid ground as the only few ladders out of water were missing/broken. I believe I remember of a graveyard which had an exit - possibly accessible - blocked by tombstones.