All* areas** in Project Eternity should have more than*** one entrance****.
* = Obviously, we can tolerate a minority of areas having only one entrance
** = City, castle, forest, building, level, room. From macro to micro.
*** = Two is minimum. Three or more is even better.
**** = Entrance can be literal or figurative. An entrance can be a second door, or a sewer you can crawl through to get underneath a building, or using a roof, or using magic to teleport into an area, or using dialogue or a disguise or other unique thing to gain access into an area.
Sure, having 100 entrances to one room would cease to make that room a room (maybe swiss cheese), so perhaps not all entrances should be "literal" holes in a wall, and perhaps we should limit the number of ways into an area, so that strategy is required. But having multiple ways to approach entering a part of the game, the more complex that game is by nature.
Of course, this can extent to exits as well, but I think "how you got there" is slightly more important than "how you left".