My current fortress is quite nicely located on a cliff (I only had to remove a few upward slopes for further impenetrability). But the very first immigrants arrived from the direction that was inaccessible in the first place, as far as I can tell. Had to build a bridge for them, never used it since, stays retracted. Now, two years later, the last wave arrived from behind the river. That river does stay frozen for good half of the year (I had a dwarven caravan arrive from the same direction while it was frozen), but those stupid dwarves arrived in Malachite, so I'm building a bridge again (3-tiles wide, just in case caravans are stupid too). Screenshot is included.
Is that a bug, or known behaviour or what, that bridge building is starting to annoy me. I'm a low to medium experience DF player (had about 20 fortresses but yet to survive my first siege) and have never seen this before, migrants always arrive from reasonable places.