Río San Lorenzo flows through the Ledesma Department of Jujuy Province in northwestern Argentina, draining into the San Francisco River as part of the broader Bermejo River basin. This subtropical river winds through a region of remarkable ecological diversity, transitioning from montane terrain into the lowland yungas forest zone — one of South America's most biodiverse ecosystems. The river's character shifts considerably along its length, moving from faster, boulder-strewn upper reaches into broader, slower-moving lower sections as it approaches its confluence with the San Francisco. The surrounding riparian corridor is lush and densely vegetated, reflecting the high rainfall and humidity characteristic of the yungas, and the river's waters carry the tannins and sediments typical of a freestone system draining forested slopes.