A Hidden Doorway
Hidden doorways are a common worldbuilding element. Often, these are found behind bookcases, tapestries, fireplaces, or made to look like the wall or stone on which they reside. Sometimes maps or clues will lead to their location. They may be opened with a secret word, phrase, or by using a hidden lever or button. Hidden doorways may lead to a secret chamber, hidden lair, portal, or secret exit.
When designing secret doorways consider who knows of their location, who built them and for what reason, how they are opened, and where they lead.
Someone needs to go back for a torch.