The Treasure of Aunt Masroura

There are many chambers in “Aunt Masroura’s” old house. There is one locked room that no one can enter but herself! The children think that there is a treasure in that room. Are they right? But “Aunt Masroura” is very poor, form where does she get her treasure? What is the reason that urged “Aunt Masroura” to open her room for all children?