DerekSTheRed
Explorer
If I was writing a monster lair/fortress/city in pre-4E, I would think about it in terms of monster's point of view. I would design the lair/fortress/city in such a way as the monsters thought would best be defended. For example of this, the City of the Spider Queen listed rally points for the other Drow defenders to assemble before tracking down the PCs after an alarm was raised. I then let the PCs assault the lair/fortress/city. Smart PCs would recon and plan out their assault. This planning would be par of the fun as the PCs debated strategy.
In 4E, this would be designed differently. In the modules I played it would end up being pretty linear. This is because each encounter needed to be a challenge and once you spent all that time creating a challenging encounter, you wanted the players to experience it. One could mitigate this linearness somewhat. For instance, in Assault on Nightwrym Fortress, the PCs had to get three MacGuffins which they could do in any order. They still ended up going through the exact same three encounters though.
In 4E, this would be designed differently. In the modules I played it would end up being pretty linear. This is because each encounter needed to be a challenge and once you spent all that time creating a challenging encounter, you wanted the players to experience it. One could mitigate this linearness somewhat. For instance, in Assault on Nightwrym Fortress, the PCs had to get three MacGuffins which they could do in any order. They still ended up going through the exact same three encounters though.