In the late 70's/early 80's, there was a restaurant chain called "The Big Yellow House". It was a big two-story buliding, shaped like, well, a big yellow house.
They were all built exactly the same, and in each of them, the restroom (the mens', at least) had this little door in the wall, maybe 3 feet tall. It was probably some sort of storage area or something, but I imagined that it was some sort of secret passage that led to a magical world. I always tried the knob whenever I went in there, but alas, it was always locked.
A childhood belief about excursions

others believed things like this
- I used to believe there was a secret door to the gremlin world hidden under my bed— Mel
- When I was littler I thought that Santa had a magical key that could let him get inot everybody's house— Eric "The Santa Jr. Looking guy"
- I used to believe that, in a deep and profound kind of way, the words "door knob" rhymed with "said so". — Katie
- I used to think that Hadrian also built the Great Wall of China.— Spacey
- I used to believe that when you moved house you swapped house with the person moving into your old house.Anon
- I used to believe that if i behaved badly i would be taken away in a yellow van.— Mattio