The Argentinean side of the falls and the surrounding rainforest are contained within the Parque Nacional Iguazú (tel. 37/5742-0722, www.iguazuargentina.com , 8 a.m.–6 p.m. daily, 18 pesos). Although it receives fewer visitors than its Brazilian counterpart, it boasts a larger number of cataracts as well as more vantage points from which to observe them up close. Make sure to bring a bathing suit as there are pools in the river that are ideal for taking a dip.
If you have a car, getting to the Argentinean park is quick. The distance from Foz  to Puerto Iguazú  is 23 kilometers (14 miles), then follow Ruta 12 for 5 kilometers (3 miles) to the park entrance. Without a car, it’s easy but somewhat time-consuming to get to the park from Foz. If you’re pressed for time, you’re better off joining a Brazilian excursion organized by some of the travel agencies and hotels in Foz.
Alternatively, buses make the 30-minute trip to Puerto Iguazú, leaving at 45-minute intervals from the local rodoviária in Foz. From Puerto Iguazú’s bus station, hourly buses make the 30-minute trip to the park’s entrance. If you don’t have Argentinean pesos, you can pay for your bus fare and all fees within the park (including food and drinks) with Brazilian reais or U.S. dollars.
At the entrance to the park is a visitors center with souvenir shops, a café, a restaurant, and the Centro de Interpretación de la Natureza, a natural history museum that provides a good introduction to the region’s flora and fauna. From here, at 25-minute intervals, mini trains shuttle you through the forest to the falls.
The first stop is the Estación Cataratas, point of departure for two easy walking trails. The 900-meter (2,950-foot) Circuito Superior trail is at eye level with the top of the falls—catwalks allow you to actually walk behind some of them. The Circuito Inferior is a 1.5-kilometer (1-mile) circular trail that meanders through the forest and gives you a vision of the falls from below.
A highlight is the free boat trip that takes you across the river to the Isla San Martín, where a lookout point offers a terrific view of the Argentinean falls. You’ll also find natural pools where you can swim.
The second train stop is the Estación Garganta del Diablo. From here, a 2-kilometer (1.2-mile) trail follows the Rio Iguaçu upstream to the Garganta del Diablo (Devil’s Throat), where you’ll be treated to the spectacular vision of 14 separate falls flowing together to form the most powerful waterfall (in terms of volume of water flow per second) on the planet. Although you’ll be completely drenched, the sensation is absolutely otherworldly. Aside from spume and spray galore, you’ll see multiple rainbows, butterflies, and kamikaze-like swifts making vertical dives from cliffs to snatch insects out of the air.
Located within the park’s visitor center, Iguazú Jungle Explorer tel. 35/5742-1600, www.iguazujunglexplorer.com ) is an ecotourism agency that offers guided hiking tours through the park along with boat trips up the Rio Iguaçu rapids that will bring you thrillingly close to the falls.