ooc: Wow, nice rolls.
You find the obligatory loose brick with little effort. When you press it, a portion of the northern wall slides away, revealing the passage within. It is, if anything, in a state of even greater disrepair than the rest of the tunnels, but it doesn't look like it's going to collapse any time soon. From where you are, you can see that it continues for about a dozen yards before terminating in another wall. A nearby switch indicates that this is not the dead-end it might otherwise appear to be.