Sounds incredible. I am going to bookmark this to do if I take a trip to Brazil.

Seconded enthusiastically. That dam tour is amazing. Did it in 2007 or so.

Expect potential weirdness though. My wife was wearing a (not particularly short) skirt, and the lady at the office selling tour tickets made her step back and spin around, then said she couldn't go in like that. There is a gift shop that sells dam branded pants, so she bought a pair and we were cleared to go in. After all that, one dude in the control room was watching soft-core porn on one of the control room computers.

The turbine shaft room is especially crazy, since they let you (at least back then) walk right up to a few inches away from the shaft mechanically transmitting 700 MW of power! You could reach out and touch it, but we didn't and I wouldn't recommend it.

Long skirts (or other loose clothing) around big, spinning mechanical load transmission elements are an easy way for the rest of your life to become a cautionary Youtube video on workplace safety.

Seconding this! Make sure you get the "special tour". It was an absolute highlight of my trip. If you are interested in power infrasture it's a must see. If you're afraid of heights, perhaps not so much.

Could you kindly elaborate on the "afraid of heights" aspect? Was there a lot of catwalks or anything of that nature?

There is one part where you are invited to walk on a catwalk that's very high up (an outdoor staircase sort of like a fire escape). My recollection is that walking on it is not mandatory for the tour, but I'm not absolutely certain of that.

You're also invited, but not required, to look over the edge of the dam from the top, which is also very far down.

This is correct. If you don't like heights, that's definitely not a reason to skip the tour, but you'll miss out on one piece (that I enjoyed).