Pausing for a moment to collect their thoughts, the party thinks back to the night before, when Manzanita questioned the prisoner. When Manzanita offered to spare his life and release him with equipment, he did not look too thrilled at the thought, glancing nervously around at the darkness. Nonetheless, he talked.
According to the half-orc, there was only one room up the mountain, the lookout room the party is in now. The half-orc seemed to have trouble with counting, but he thinks there are six more of his compatriots left. These were on guard duty, beyond the corridor with the spikes. The spikes in the ceiling of the corridor are a portcullis, but he's never seen them used. He knows that if the fort is discovered, he's supposed to move behind the portcullis, towards the barracks area (the area you explored). He doesn't know where the winch controlling the portcullis is. The main entrance is past the snake pit. The wall beyond the snake pit is not natural (rock, earth and shrubs), but is a moveable wall. The wall can be moved aside and a bridge installed over the snake pit. Beyond the false wall are two large chambers before the corridor with the portcullis. From the main entrance, the first chamber is a guard post, and the second chamber is filled with crates.