I don't remember what age this was around but I used to believe that restrooms were rooms with several beds in them that people could lie down in when they got tired.
A childhood belief about sleeping

others believed things like this
- I used to believe that flowerbeds were beds for flowers.— Nina Green
- I believed that teachers lived in rooms above the school gym.— Kelly
- I used to believe that the short display beds at department stores were for dwarfs.— p
- I used to believe that snow on the ground was clouds that were too tired to fly.— alex
- I used to believe that being wasted meant feeling really tired. Anon
- Does anybody remember that song "OUT OF REACH" well i remember i used to sing it as "BATTEERRRRYYY". — meeeeeeeee