Recall from
tip #1 that we were wandering aimlessly around Italy, visiting anything interesting that we noticed in our path.
Well, in Florence, we noticed this rather remarkable dome:

On one entrance, there was a sign that said "Visit the dome."
Sounds interesting, we thought.
Now -- this is perhaps silly of me -- but my initial assumption was that this was just an entrance to go into the cathedral "Il Duomo" and look up at the dome. Then, as we were buying our entrance tickets, I noticed a sign that said there were four-hundred-sixty-three stairs, hence the visit is "not appropriate for people with heart conditions." That warning went right past me. I don't have a heart condition, and I can climb four-hundred-sixty-three stairs without the slightest difficulty.
It wasn't until I'd passed the point of no return that it hit me that this wasn't
quite the same as climbing four-hundred-sixty-three stairs
in a modern stairwell.
The problem is that the path to the dome is a long, dark, narrow, cramped stone tunnel. There's a huge line of people in front of you and behind, and the corridor is so narrow that two people can't pass each other (except in a handful of isolated wider points). In particular, you can't turn around and go back out the way you came -- the only way out is to continue to press forward through the cramped tunnel, and who knows what's up ahead??
I normally think of myself as only
mildly claustrophobic. (Of course I had a weirdly similar scare at that
polygamist church service...) Even before I got to see the dome, I was already starting to get very, very nervous. If someone were to have a heart attack in the middle of the visit --
which I could totally see happening!! -- how could that person (and everyone else) be evacuated?
Then we stepped out onto the balcony of the dome:

It's actually quite amazing! It's apparently the largest purely-masonry dome in the world. Here's looking up:

And here's looking down:

This is why, naturally, you don't want someone freaking out, ruining the visit for all of the normal people.
The balcony along the inside of the dome is made of stone, but is encased in glass, and is still so narrow that it isn't possible to pass anyone. And it was rather unfortunate for the tourists ahead of me in line -- who wanted to stand there at leisure admiring the ceiling -- when I gently suggested that they
please step away from the exit because I have to get out of here
now.
I climbed down the earliest exit possible (there were only two choices), but my husband continued on up the second path to the visit to the outside terrace:

If it had been necessary to go up there, I'm sure I could have done it without a major incident. But I'm glad I didn't have to, and
boy was I ever happy to be out of that towering dungeon and back on solid ground in the great out-of-doors!
Later we happened upon a museum of medieval torture devices. On that one, they were careful to post a warning that the visit wasn't recommended for people who are "very sensitive or claustrophobic." Of course, merely by reading that it's a display of medieval torture devices, I already know I don't want to see that.
But I appreciated the careful warning. ;)