Before you stands a large black spire. It reaches easily ten miles up into the air, and it's base is large, you estimate with your amazing DM reading from notes math, that it is probably about a mile in diameter. Smooth and polished black stone is the entire outside surface, with but a single entrance, a large curved arch that extends like a hallway several hundred feet, descending at a slight incline into darkness.
The floor too is of the same black rock, and though it appears slippery, it seems to allow for measured descent. A small engraving on the floor just inside the entrance says merely, "Welcome. Wash your feet." repeated in several languages (Common, Undercommon, Draconic, Celestial, Infernal, Abyssal, Sylvan, and a language you do not recognize in that order).
[spoiler]And you all need to write down your languages, because seriously one out of the six of you have them.[/spoiler]