The sinking sands (LBT 2)
The burning mountain (with the crater being referred to as the "gurgling pit" if memory doesn't cheat me) (LBT 2)
The bubbling muds (LBT 6)
There are also a number of notable locations which are never given a real name in the movies, e.g. the place where the grownups meet in LBT 7, a couple of "lookout ledges" from where you have a good view into the mysterious beyond (LBT 3 and 4). The different passages into the Mysterious Beyond etc.