The Your Sanctuary locations are things that are guarded my strong enemies. These are basically a tune that gets recorded on the Sound Stone.
This is an area on the top of a mountain in Onett.
This is an area inside a cave in Happy-Happy Village.
This is an area inside a cave located in Saturn Valley.
This is an area located inside a cave which can be found North of Winters.
This is an area located above the sewers of Fourside
This is an area located underneath Dalaam
In a cave beneath Tenda Village
This is an area located in the Lost Underworld
These appear as a Bright, Shining Light that is guarding a door. The light will talk, and then you will have to fight the Your Sanctuary Guardian. It will say that it is their location now, and you have to try and take it from them.
 Monsters Usually Located
Monsters like the Mobile Sprout, or a variation of that monster will usually appear in all of them. A few other things like the Mole Playing Rough and Mighty Bear will appear in different locations as well.