OOC: I'm going to push this along — climbing's fun, but the fun, I think, won't last forever. Plus, death by falling is not very pulpy or hard-boiled. Unless you jump...
Gannon grabs the rope and is able to climb down the rest of the way. The rest of you manage to follow with little to no problems.
The tunnel eventually slopes enough so it can be walked in (which is good, considering there wasn't an inexhaustible supply of rope). The shaft itself is a crumbling mix of ancient stone and earth, and as you climb deeper (and reach the light source you had thrown down), you begin to notice centipedes and other insects covering the walls.
After long descent, the shaft opens up into a vast chamber, some six feet above the chamber's floor. The ruins of nearby walls and buildings appear as a network of deep shadows, and you can't quite gauge the actual size of the cavern. A change in air pressure and air currents, however, indicates that the space is as vast as it feels from the tunnel entrance.