This spectacular landscape of crashing waterfalls was once held sacred by the Guarani people, who called it Iguassu, or "Big Water." Straddling the border of Brazil and Argentina, Iguassu Falls is an incredible natural attraction of 275 waterfalls of various sizes, making it a UNESCO World Heritage Site and one of the Seven Wonders of the World.
Puerto Iguazu is the Argentina gateway - from here you can tour the Brazilian side, tour both sides and take other sightseeing tours to nearby attractions like the San Ignacio Mission or the Itaipu Dam on the Brazil-Paraguay border.
While Argentina, with 80% of the falls, has more trails and activities, the Brazilian side, with tours leaving from Foz do Iguacu, offers the finest views. Pedestrian walkways descend into the fierce rainbow-strewn mists of Fiorano Falls, and take in panoramic vistas over the massive flowing curtain of Rivadavia Falls, which cascades across a plateau.
Iguacu Falls is not the only natural wonder in this amazing neighborhood. Just 10km (6mi) from Foz do Iguacu, massive Itaipu Dam was, until recently, the world's largest man made structure (since eclipsed by China's Three Gorges Dam) and is still the world's most productive hydroelectric facility.
The dam is considered one of the World's Seven Modern Wonders, clocking in at 7.2km (4.5mi) long, 65 stories high, with a maximum flow more than 40 times that of Iguacu Falls on a good day.
In fact, Itaipu marks the spot where an almost equally epic cascade was once the centerpiece of Guaira Falls National Park. The "Seven Falls of Guaira" (actually 18 cascades on the Parana River, gushing twice as much water as Niagara Falls) were drowned in 1982 when the dam was under construction. The national park was dissolved, the cliffs dynamited underwater to ensure safer navigation on the new reservoir, and today Itaipu produces more than 20% of Brazil's electricity.
Iguassu 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.
Originally erected in 1903, the memorials are built around three simple cement obelisks, painted in the patriotic colors of the three respective flags. The view is nice, and all three monuments are surrounded with vendors selling snacks and souvenirs. The Argentine landmark has the distinction of being the easiest to visit, a pleasant walk from the city center along the riverfront.