The Ring includes the Ring-wall and the sections within, as well as the inhabitants.

"A great ring-wall of stone, like towering cliffs, stands out from the shelter of the mountain-side, from which it runs and then returns again... one who passes in and comes at length out of the echoing tunnel, beholds a plain, a great circle, somewhat hollowed like a vast shallow bowl: a mile it measures from rim to rim.

"It is green and filled with avenues, and groves of fruitful trees, watered by streams that flow from the mountains to a lake. There stands a tower of marvelous shape. It was fashioned by the builders of old, who smoothed the Ring of Isengard, and yet it seems a thing not made by the craft of Men, but riven from the bones of the earth in the ancient torment of the hills. A peak and isle of rock it is, black and gleaming hard: four mighty piers of many-sided stone are welded into one, but near the summit they open into gaping horns, their pinnacles sharp as the points of spears, keen-edged as knives. Between them is a narrow space, and there upon a floor of polished stone, written with strange signs, a man might stand five hundred feet above the plain." Tolkien

"Many houses there are, chambers, halls and passages, cut and tunnelled back unto the walls upon their inner side … Thousands could dwell there, workers, servants, slaves and warriors with great stores of arms; ((wolves were fed and stabled in deep dens beneath.))" (Note: this was during the time of Saruman, however it's fairly reasonable to assume that in times before these inside chambers had been hewn for the use of the military and adapted/converted after time passed.)

Delving directly into the volcanic rock, the Númenoreans built what amounted to an entire city within the base of the wall. There are quarters for an army there, with many halls and chambers, as well as stables, armories, and smithies. A tunnel two hundred feet long and thirty five feet high was cut through the ring-wall; this tunnel forms the sole commonly known entrance to the interior plain.

If you are standing halfway to Orthanc and turn back to stare at the Gate what do you see? Well, you see three tiers, including the bottom one, the top narrower than the middle and bottom. You'd see plenty of exterior steps, all stone, with plenty of arches and statues and the details that mark out the Numenorean wonders now lost. 3,000 years ago this place gleamed. There were no limits. Think of the really majestic parts of Minas Tirith - that's this place. If you've seen Egthela you'll see I tried to reflect a lot of that there in the Garrison area with the Pipe House and general architecture. This was to be a military base, but that never stopped the Numies from turning out something incredible.

Imagine staring over your shoulder at a 500 foot high tower in the middle of a lake, leading back to the Gate and other avenues like spokes from the middle, with thousands of stairways, statues, windows, gates, etc. What you won't see though is housing outside the Ring-wall. There are no stalls or houses or stables or anything like that - it's all within the wall itself. Why? It has always been that way. That is why. The inner area is lush and filled with small orchards, fish ponds, streams, grazing areas for small flocks, gardens etc. It's beautiful.

The ring-wall is more than one hundred feel high. its outer surface is sheer; all cracks and fissures were filled in by the Númenoreans. The top of the wall is eighty feet wide; a level road runs around the circumference on top. The rim of the wall, though not crenelated, is raised into a lip about five feet above the surface of the road, sufficient to give the defenders ample protection.  Embrasures occur at regular intervals; guard towers are unnecessary because a good-sized army can camp on lop of the walls in the event of an attack.