Eldon is still invisible so he continues onward towards the gates, though stays close enough to let his companions catch up, and not get too far ahead of them. 

Past the gate, the cave opens up to an enormous circular hall beneath the mountain, about 350ft high, with the end at an estimated half mile away from you.
From the gate further into the cavern the ground shifts into a slope with the old dwarven city buildt on this "hill".
Eldon can make a perception check.

Swol growls at the foolish goblin making all the noise. “Quiet now or I eats you.” He then stalks forward still seeking prey. 

Reelq slowly walks forward with his Pepperbox in his hand, keeping to the cieling so that he can keep track of all his companions.

Reelq can certainly stick to the ceiling, though it might not be the smart move. The ceiling arches up to a dome, about hight in height, so to get to your companions you'd either have to survive the fall or run 0.6 miles(at max) to get to them. its your decision.

(Any sign of more goblins?)

Not in the close area. i will provide a map in some time that shows the area with the estimated outposts

Ok so the map together with the notes to the puzzle box will take more time. sorry about that.

But regardless of that, we should be able to continue.

Eldon perception: 23

(Sorry for the delay.)

As eldon steps into the "city hall" he gets an impression on how the city is build. or rather was built. the buildings are grouped into blocks, those blocks seperated by wide streets. within, the roads are much smaller, just wide enought for two wagons to pass.
On your left side, the river reemerges out of the cave wall and flows through the city in a dwarf-made canal. You also hear a waterfall in the distance.

Eldon waits for the others to catch up, then will follow them which ever way they are headed. He stays invisible.

Reelq will move to join with the others but will go back onto the cieling at the first chance he gets so he can get an overview of what is around them.

Swol starts searching for any sign of goblins or their tracks. 

Roll a survival check for Swol

Swol Survival : 5

Swol does not see any tracks in the area. But as the city is ruined, many of the smaller roades gmhave been blocked by debris, so its safe to assume that the goblins took the main roads for the most öart of thir travel in the city

There is less rubble in the main roads. But the posts are not set on those main roads, so a stealthy approach will be rather easy