Those who have gotten to the corner can see that the room is shaped like the inside of a sphere, 80' in diameter. On turning the corner, you are facing steeply "downhill" by your current orientation. You can attempt to realign your subjective gravity and/or make a DC 12 balance check to avoid tripping as you head down the steep slope. There is a large stucture jutting out into the dome on one side, and several small passages lead out into the surrounding rock.
The structure seems to have windows, though they will be hard to see until Charlarn gets his Sunrod up to the corner.
Also, remember that at this time you can only make out the dwarves if you have low light vision or darkvision. For the time being, only low light vision (and not darkvision) allows you to see the far side of the dome.