This place has a natural stone bridge that one can walk over to the other side. It holds the gab between a very long drop. Cera mentions once that it'll take most of the day to get there so it must not be near by. One is also visible in the 8th movie towards the end and it's near a natural hot spring(s) that Littlefoot and his friends find with Mr. Thicknose.
The Great Stone Walkover appeared in two major parts: one, The Land Before Time film 'The Big Freeze' which it is clearly visible towards the end of the film and it is near a natural place as Littlefoot, Cera, Ducky, Spike and Petrie are finding Mr. Thicknose. For number two, it's in the twentieth episode of the LBT called 'The Big Longneck Test' where Shorty and Littlefoot's friends are going on the other side of the valley.