fusangite said:
I'll offer an exception to that experience. I wasn't railroading anyone when I decided there were only two secret caves in a cliff face I made. But my players kept looking for more for the next 3 hours of playing time.
Hmm... Quote feature doesn't seem to include my text. Hopefully context will be obvious to anyone paying attention!
I would say that is more a difference in playing style, one option of which can be termed "rail-roading" but is really "moving the game forwards".
I've had similar experiences - a session the other week was basically three hours of the players working out how to get into a city occupied by enemy forces without being killed. In fact, the enemy forces were there as "peace-keepers" and the worst thing that happened to them was a lot of red-tape. (Initially...).
In your example, one could say "okay, you search for many hours and eventually you are pretty certain that the only ways in are here, and here." Or you can ask where they are going to search and run it that way. Either is valid, depending on style. Neither is rail-roading.
As for limited choice, that in itself isn't rail-roading, but it gets confused. Someone up thread mentioned the typical dungeon T-junction, and this is similar. Choices are limited - the PCs either go left, right, or back the way they came. However, they still have the choice, limited though it is. A lot of other dungeon staples are the same - pull the level, don't pull the lever (with all the spin-off possibilities - use Mage Hand to pull the lever, *push* the lever etc. etc.) Railroading would be that, no matter what the players do with the lever, the same thing happens.
*That's* the kind of subtle difference that seems to be lacking a phrase. Perhaps Menu-gaming, or something like that, to indicate that choice is finite and explicit, but still a choice nonetheless.