Mystery Locks: Mysterious Castle

You chose to leave the group when everyone was staring at another empty room in the castle, like it was the best thing they have ever seen. You noticed a "Do not enter!" wooden door that seemed to be ten times more interesting and intriguing, so you decided to take yourself on a little adventure. When you pushed it, a dark circular stairway unveiled in front of your eyes. Where could they go? You could never know if you would keep standing there.