I remember hearing someone say the additional watches were compasses or something similar for artillery, but its been too long for me to remember anything about where I heard it.

What happened to PPB? I haven’t seen it in a while despite a ton of PPB worthy posts

I wonder if largest meant “most people in a building”?

Did anyone else feel like the second Act of threads was a lot weaker than the first?

It is not, these control rooms are rather central to the plant. If I am not mistaken this is the reactor 4 panel, and immediately to the right of this image is the original concrete sarcophagus. The plant still has electrical power for some of the monitoring stuff, and the lights are still on (at least last I knew about) for maintenance and tour groups.

Here is another angle with the lighting and concrete visible. As you can tell, the concrete on the left is not the same type as the ceiling.

The control rooms for reactors 1-3 are still in pretty decent shape, as they were operating much after the meltdown. There are also schematics available online if you want to see how these rooms are positioned within the plant.

Java/C# would have types before the variables:

double sum = 0d;
for (int i = 0; i < 4; i++)
	sum += 3 * i;