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.

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.

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