Here, we see what the adventurers saw when they opened the bronze doors in the floor: a spiral stone staircase around a central shaft, 180 feet total depth total, but I said something about it looking 150 feet deep. The stairways are 10 feet wide, with a 30 by 30 foot open space in the center, so the shaft is 50 by 50 foot total. You can also see that each flight of stairs has a square landing in the corner.
Here's a side view of the shaft. We can see that the first flight of stairs ends suddenly; the second flight, which should be along the west wall, is completely missing, probably broken in some horrific battle now long forgotten. The third flight (along the north wall) and all further flights of stairs are intact, however.
Each flight descends 30 feet, so the last step of the first flight of stairs is 30 feet away and 30 feet above the first step of the third flight of stairs. Quite a jump! Assuming someone could make the horizontal distance, that's still 3 dice of damage. Missing the jump would mean a 150-foot fall and 15 dice of damage. It's only 120 feet down from the end of the first flight to the landing at the top of the last flight, though. Any of these jumps would have helped me to introduce my injury system!
Fortunately, the party didn't try to jump, but instead tied together three ropes and anchored it to a larger timber that had been used to bar the door down into the shaft. I was kind of skeptical of the way they wedged the timber against a wall, but they made it down to the landing at the top of the last flight of stairs. I'm not sure why they didn't use spikes; I don't think they brought any, but the timber had been spiked to the floor, so they had at least two spikes.
The stairs are kind of steep. Most stairs are at a 30 degree slope, but I've been using 45 degree slopes in my maps, because it makes things easy. There are real-world stairs with a steeper slope, like steps on a Mayan temple, but those are unusual.