Glancing around the corner, the dwarf sees that the passage continues south for 30 feet, before heading down, presumably a stairway.
Marcus examines the panel. After scraping away some grime, he can see that it was once an ornate panel, though what is was displaying cannot now be determined. The mechanism is similar to the other one the party examined & opened, and the Gypsy is confident he can open it without mishaps. Removing a couple key bricks, he is able to shove the panel aside.
Behind it is a 5 foot wide coridor heading south for 30 feet, to a dead end. The dust is heavy, and Marcus suspects this door hasn't been used for centuries.