You're now facing the wall. Turn around and walk slightly towards your right to the open wooden door in the extreme right. Just before that door, turn left and walk straight towards the entrance. There you will find the stairs in the right side. Get on the stairs, then turn around after reaching the first step. Now get down, move slightly towards left and then turn around again. Now get on the stairs once again, move forward and stand at the entrance of the stairs facing the wall, you will reach your destination.