Mercedes is a village in Corrientes in Argentina. It's a pretty nondescript town that strictly sticks to siesta. However, to visit Esteros del Ibera and Colonia Carlos Pellegrini it's the place to get a transport and also organise your stay and activities in Carlos Pellegrini though not necessary.
The options to get in are few. There are direct buses from Parana in the South, Corrientes in the North and Paso de los Libres (on the Buenos Aires - Puerto Iguazu line).
One Bus Monday to Saturday to Colonia Carlos Pellegrini at around noon. 25 Pesos and about 3 hours on a dirt road. Book in advance at the hostel or the terminal.
2nd-order administrative division
Primary administrative division