Both sides of the river--Paraguay and Brazil--have visitor centers and offer tours of their facilities. I only saw the Paraguayan side. They claim they have lots of tourists, but I guess I came on an "off" day--I was the sole visitor in a 47-passenger bus, but got the VIP treatment anyway. There is no one vantage point from which to get a spectacular view of the whole project, but you do get to stop and see parts of the interior and exterior of the dam.
Quick Tips:
It is a very practical side trip for anyone visiting the Iguassu Falls area. You can take a tour, or make it on your own, which is what I prefer to do. From Foz do Iguassu, Brazil, take one of the many buses to Ciudad del Este, across the river in Paraguay. This is a major international commercial (and smuggling) center, so if you're a shopper, check out the bargains. To get to the Itaipu project by bus, it is necessary to catch a bus marked Hernandarias. Tell the driver you want to get off at Itaipu. To return, cross the highway and catch a bus going back to Ciudad del Este in the other direction. Note that Paraguay is one hour behind both Argentina and Brazil, so that it is easy to get confused about timetables and opening hours if you don't keep this in mind.Best Way To Get Around:
I would not suggest my method to anyone not comfortable navigating in Spanish. Travel agencies in the three-country border area sell organized tours which would be a better bet to someone without Spanish ability.