Arroyo Mártires Grande is a low-difficulty stream running through the subtropical forest of Misiones province, located near the small town of Mártires, roughly 28 km from Oberá and 68 km from Posadas. The stream sits within an ecological reserve characterized by dense native vegetation and a wide variety of flora and fauna typical of the Misiones jungle.

A local operator, YASÝ, Selva & Agua, runs guided kayak excursions on the arroyo, departing from their base on Ruta Provincial 103 at the Puente Arroyo Mártires Grande. Their standard route covers approximately 4 km on the water and is rated low difficulty, making it accessible to paddlers without advanced technical skills. The excursion can be combined with a 2 km trekking segment through the surrounding forest, offering a closer look at the area's biodiversity. Reservations require a minimum of two people.

The CostaVerde facility, situated about 300 meters from Ruta Provincial 103 and extending across 27 hectares, provides camping and additional access to the stream. The property includes swimming spots at stream sections and small waterfalls, farm walks, and wildlife observation. It is positioned approximately 4,600 meters from Ruta Provincial Nº 4 at Km. 78.

The stream's water takes on green tones consistent with the heavy forest canopy overhead. The surrounding reserve supports diverse animal species, and the area is noted for clean air and a natural soundscape. The overall character of paddling here is calm and immersive, suited to those interested in the ecology of the Misiones jungle as much as the paddling itself.