Igacu Falls are famously shared between three nations: Brazil, Argentina, and tiny Paraguay (which doesn't actually claim any part of the primary falls, only the rivers). Though the actual Tripitarte, or triple border, lies unmarked at the deepest part of the confluence of the Iguazu and Parana Rivers, all three nations have erected monuments—built around obelisks painted patriotically with the colors of their respective flags—overlooking the spot.
Brazil's Hito Tres Fronteras (Three Borders Landmark) was originally erected on July 20, 1903, overlooking the pretty scene and international bridges. Though it sits on the outskirts of Foz de Iguacu city, it does bring in tourists, as well as vendors selling souvenirs and snacks. Next door, the Space of the Americas tourist complex offers meals and views in more relaxed environs.
The Brazilian monument is located 6km (4mi) from the city center; you can catch colectivos, but it's safer and easier to take a taxi or tour. While most operators recommend visiting landmark around sunset, be aware that this neighborhood can be a bit sketchy after dark. The obelisk on the Argentine side is much more accessible.